// Render with Asciidoctor = Babeltrace{nbsp}2 contributor's guide Jérémie Galarneau, Philippe Proulx 1 December 2020 :toc: left :toclevels: 3 :icons: font :nofooter: :bt2: Babeltrace{nbsp}2 :c-cpp: C/{cpp} :cpp11: {cpp}11 This is a partial contributor's guide for the https://babeltrace.org[{bt2}] project. If you have any questions that are not answered by this guide, please post them on https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev[Babeltrace's mailing list]. == {bt2} library === Object reference counting and lifetime This section covers the rationale behind the design of {bt2}'s object lifetime management. This applies to the {bt2} library, as well as to the CTF writer library (although the public reference counting functions are not named the same way). Starting from Babeltrace{nbsp}2.0, all publicly exposed objects inherit a common base: `bt_object`. This base provides a number of facilities to all objects, chief amongst which are lifetime management functions. The lifetime of some public objects is managed by reference counting. In this case, the API offers the `+bt_*_get_ref()+` and `+bt_*_put_ref()+` functions which respectively increment and decrement an object's reference count. As far as lifetime management in concerned, {bt2} makes a clear distinction between regular objects, which have a single parent, and root objects, which don't. ==== The problem Let us consider a problematic case to illustrate the need for this distinction. A user of the {bt2} library creates a trace class, which _has_ a stream class (the class of a stream) and that stream class, in turn, _has_ an event class (the class of an event). Nothing prevents this user from releasing his reference on any one of these objects in any order. However, all objects in the __trace--stream class--event class__ hierarchy can be retrieved from any other. For instance, the user could discard his reference on both the event class and the stream class, only keeping a reference on the trace class. From this trace class reference, stream classes can be enumerated, providing the user with a new reference to the stream class he discarded earlier. Event classes can also be enumerated from stream classes, providing the user with references to the individual event classes. Conversely, the user could also hold a reference to an event class and retrieve its parent stream class. The trace class, in turn, can then be retrieved from the stream class. This example illustrates what could be interpreted as a circular reference dependency existing between these objects. Of course, if the objects in such a scenario were to hold references to each other (in both directions), we would be in presence of a circular ownership resulting in a leak of both objects as their reference counts would never reach zero. Nonetheless, the API must offer the guarantee that holding a node to any node of the graph keeps all other reachable nodes alive. ==== The solution The scheme employed in {bt2} to break this cycle consists in the "children" holding _reverse component references_ to their parents. That is, in the context of the trace IR, that event classes hold a reference to their parent stream class and stream classes hold a reference to their parent trace class. On the other hand, parents hold _claiming aggregation references_ to their children. A claiming aggregation reference means that the object being referenced should not be deleted as long as the reference still exists. In this respect, it can be said that parents truly hold the ownership of their children, since they control their lifetime. Conversely, the reference counting mechanism is leveraged by children to notify parents that no other child indirectly exposes the parent. When a parented object's reference count reaches zero, it invokes `+bt_*_put_ref()+` on its parent and does _not_ free itself. However, from that point, the object depends on its parent to signal the moment when it can be safely reclaimed. The invocation of `+bt_*_put_ref()+` by the last children holding a reference to its parent might trigger a cascade of `+bt_*_put_ref()+` from child to parent. Eventually, a **root** object is reached. At that point, if this orphaned object's reference count reaches zero, the object invokes the destructor method defined by everyone of its children as part of their base `struct bt_object`. The key point here is that the cascade of destructor will necessarily originate from the root and propagate in preorder to the children. These children will propagate the destruction to their own children before reclaiming their own memory. This ensures that a node's pointer to its parent is _always_ valid since the parent has the responsibility of tearing-down their children before cleaning themselves up. Assuming a reference to an object is _acquired_ by calling `+bt_*_get_ref()+` while its reference count is zero, the object acquires, in turn, a reference on its parent using `+bt_*_get_ref()+`. At that point, the child can be thought of as having converted its weak reference to its parent into a regular reference. That is why this reference is referred to as a _claiming_ aggregation reference. ==== Caveats This scheme imposes a number of strict rules defining the relation between objects: * Objects may only have one parent. * Objects, beside the root, are only retrievable from their direct parent or children. ==== Example The initial situation is rather simple: **User{nbsp}A** is holding a reference to a trace class, **TC1**. As per the rules previously enounced, stream classes **SC1** and **SC2** don't hold a reference to **TC1** since their own reference counts are zero. The same holds true for **EC1**, **EC2** and **EC3** with respect to **SC1** and **SC2**. image::doc/contributing-images/bt-ref01.png[] In this second step, we can see that **User{nbsp}A** has acquired a reference on **SC2** through the trace class, **TC1**. The stream class's reference count transitions from zero to one, triggering the acquisition of a strong reference on **TC1** from **SC2**. Hence, at this point, the trace class's ownership is shared by **User{nbsp}A** and **SC2**. image::doc/contributing-images/bt-ref02.png[] Next, **User{nbsp}A** acquires a reference on the **EC3** event class through its parent stream class, **SC2**. Again, the transition of an object's reference count from 0 to 1 triggers the acquisition of a reference on its parent. Note that SC2's reference count was incremented to 2. The trace class's reference count remains unchanged. image::doc/contributing-images/bt-ref03.png[] **User{nbsp}A** decides to drop its reference on **SC2**. **SC2**'s reference count returns back to 1, everything else remaining unchanged. image::doc/contributing-images/bt-ref04.png[] **User{nbsp}A** can then decide to drop its reference on the trace class. This results in a reversal of the initial situation: **User{nbsp}A** now owns an event, **EC3**, which is keeping everything else alive and reachable. image::doc/contributing-images/bt-ref05.png[] If another object, **User{nbsp}B**, enters the picture and acquires a reference on the **SC1** stream class, we see that **SC1**'s reference count transitioned from 0 to 1, triggering the acquisition of a reference on **TC1**. image::doc/contributing-images/bt-ref06.png[] **User{nbsp}B** hands off a reference to **EC1**, acquired through **SC1**, to another object, **User{nbsp}C**. The acquisition of a reference on **EC1**, which transitions from 0 to 1, triggers the acquisition of a reference on its parent, **SC1**. image::doc/contributing-images/bt-ref07.png[] At some point, **User{nbsp}A** releases its reference on **EC3**. Since **EC3**'s reference count transitions to zero, it releases its reference on **SC2**. **SC2**'s reference count, in turn, reaches zero and it releases its reference to **TC1**. **TC1**'s reference count is now 1 and no further action is taken. image::doc/contributing-images/bt-ref08.png[] **User{nbsp}B** releases its reference on **SC1**. **User{nbsp}C** becomes the sole owner of the whole hierarchy through his ownership of **EC1**. image::doc/contributing-images/bt-ref09.png[] Finally, **User{nbsp}C** releases his ownership of **EC1**, triggering the release of the whole hierarchy. Let's walk through the reclamation of the whole graph. Mirroring what happened when **User{nbsp}A** released its last reference on **EC3**, the release of **EC1** by **User{nbsp}C** causes its reference count to fall to zero. This transition to zero causes **EC1** to release its reference on **SC1**. **SC1**'s reference count reaching zero causes it to release its reference on **TC1**. image::doc/contributing-images/bt-ref10.png[] Since the reference count of **TC1**, a root object, has reached zero, it invokes the destructor method on its children. This method is recursive and causes the stream classes to call the destructor method on their event classes. The event classes are reached and, having no children of their own, are reclaimed. image::doc/contributing-images/bt-ref11.png[] The stream classes having destroyed their children, are then reclaimed by the trace class. image::doc/contributing-images/bt-ref12.png[] Finally, the stream classes having been reclaimed, **TC1** is reclaimed. image::doc/contributing-images/bt-ref13.png[] == Logging Logging is a great instrument for a developer to be able to collect information about a running software. {bt2} is a complex software with many layers. When a {bt2} graph fails to run, what caused the failure? It could be caused by any component, any message iterator, and any deeply nested validation of a CTF IR object (within the `ctf` plugin), for example. With the appropriate logging statements manually placed in the source code, we can find the cause of a bug faster. While <> when placing _DEBUG_ to _FATAL_ logging statements, you should liberally instrument your {bt2} module with _TRACE_ logging statements to help future you and other developers understand what's happening at run time. === Logging API The {bt2} logging API is internal: it is not exposed to the users of the library; only to their developers. The only thing that a library user can control is the current log level of the library itself with `bt_logging_set_global_level()` and the initial library's log level with the `LIBBABELTRACE2_INIT_LOG_LEVEL` environment variable. This API is based on https://github.com/wonder-mice/zf_log[zf_log], a lightweight, yet featureful, MIT-licensed core logging library for C and {cpp}. The zf_log source files were modified to have the `BT_` and `bt_` prefixes, and other small changes, like color support and using the project's `BT_DEBUG_MODE` definition instead of the standard `NDEBUG`. The logging functions are implemented in the logging convenience library (`src/logging` directory). [[logging-headers]] ==== Headers The logging API headers are: ``:: Public header which a library user can use to set and get libbabeltrace2's current log level. `"logging/log.h"`:: Internal, generic logging API which you can use in any {bt2} module. This is the translation of `zf_log.h`. + This header offers the <>. `"lib/logging.h"`:: Specific internal header to use within the library. + This header defines `BT_LOG_OUTPUT_LEVEL` to a custom, library-wide hidden symbol which is the library's current log level before including `"logging/log.h"`. + This header offers the <>. `"logging/comp-logging.h"`:: Specific internal header to use within a component class. + This header offers the <>. [[log-levels]] ==== Log levels The internal logging API offers the following log levels, in ascending order of severity: [options="header,autowidth",cols="4"] |=== |Log level name |Log level short name |Internal API enumerator |Public API enumerator |_TRACE_ |`T` |`BT_LOG_TRACE` |`BT_LOGGING_LEVEL_TRACE` |_DEBUG_ |`D` |`BT_LOG_DEBUG` |`BT_LOGGING_LEVEL_DEBUG` |_INFO_ |`I` |`BT_LOG_INFO` |`BT_LOGGING_LEVEL_INFO` |_WARNING_ |`W` |`BT_LOG_WARNING` |`BT_LOGGING_LEVEL_WARNING` |_ERROR_ |`E` |`BT_LOG_ERROR` |`BT_LOGGING_LEVEL_ERROR` |_FATAL_ |`F` |`BT_LOG_FATAL` |`BT_LOGGING_LEVEL_FATAL` |_NONE_ |`N` |`BT_LOG_NONE` |`BT_LOGGING_LEVEL_NONE` |=== The short name is accepted by the log level environment variables and by the CLI's `--log-level` options. See <> below. There are two important log level expressions: [[build-time-log-level]]Build-time, minimal log level:: The minimal log level, or build-time log level, is set at build time and determines the minimal log level of the logging statements which can be executed. This applies to all the modules (CLI, library, plugins, bindings, etc.). + All the logging statements with a level below this level are **not built at all**. All the logging statements with a level equal to or greater than this level _can_ be executed, depending on the <>. + You can set this level at configuration time with the `BABELTRACE_MINIMAL_LOG_LEVEL` environment variable, for example: + -- ---- $ BABELTRACE_MINIMAL_LOG_LEVEL=INFO ./configure ---- -- + The default build-time log level is `DEBUG`. For optimal performance, set it to `INFO`, which effectively disables all fast path logging in all the {bt2} modules. You can't set it to `WARNING`, `ERROR`, `FATAL`, or `NONE` because the impact on performance is minuscule starting from the _INFO_ log level anyway and we want any {bt2} build to always be able to print _INFO_-level logs. + The library's public API provides `bt_logging_get_minimal_level()` to get the configured minimal log level. [[run-time-log-level]]Run-time, dynamic log level:: The dynamic log level is set at run time and determines the current, _active_ log level. All the logging statements with a level below this level are not executed, **but they still evaluate the condition**. All the logging statements with a level equal to or greater than this level are executed, provided that their level is also <>. + `zf_log` has a concept of a global run-time log level which uses the `_bt_log_global_output_lvl` symbol. In practice, we never use this symbol, and always make sure that `BT_LOG_OUTPUT_LEVEL` is defined to a module-wise expression before including `"logging/log.h"`. + In the library, `"lib/logging.h"` defines its own `BT_LOG_OUTPUT_LEVEL` to the library's log level symbol before it includes `"logging/log.h"` itself. + In libbabeltrace2, the user can set the current run-time log level with the `bt_logging_set_global_level()` function, for example: + -- [source,c] ---- bt_logging_set_global_level(BT_LOGGING_LEVEL_INFO); ---- -- + The library's initial run-time log level is defined by the `LIBBABELTRACE2_INIT_LOG_LEVEL` environment variable, or set to _NONE_ if this environment variable is undefined. + Other modules have their own way of setting their run-time log level. + For example, the CLI uses the `BABELTRACE_CLI_LOG_LEVEL` environment variable, as well as its global `--log-level` option: + ---- $ babeltrace2 --log-level=I ... ---- + The components use their own log level (as returned by `bt_component_get_logging_level()`). With the CLI, you can set a specific component's log level with its own, position-dependent `--log-level` option: + ---- $ babeltrace2 /path/to/trace -c sink.ctf.fs --log-level=D ---- + Code which is common to the whole project, for example `src/common` and `src/compat`, use function parameters to get its run-time log level, for example: + [source,c] ---- BT_HIDDEN char *bt_common_get_home_plugin_path(int log_level); ---- + Typically, when a logging-enabled module calls such a function, it passes its own log level expression directly (`BT_LOG_OUTPUT_LEVEL`): + [source,c] ---- path = bt_common_get_home_plugin_path(BT_LOG_OUTPUT_LEVEL); ---- + Otherwise, just pass `BT_LOG_NONE`: + ---- path = bt_common_get_home_plugin_path(BT_LOG_NONE); ---- [[gen-logging-statements]] ==== Generic logging statement macros The {bt2} logging statement macros work just like `printf()` (except the `+BT_LOG*_STR()+` ones) and contain their <> (short name) in their name. Each of the following macros evaluate the <> definition and <> expression (as defined by `BT_LOG_OUTPUT_LEVEL`) to log conditionally. See <> and <> to learn how to be able to use the following macros. `+BT_LOGT("format string", ...)+`:: Generic trace logging statement. `+BT_LOGD("format string", ...)+`:: Generic debug logging statement. `+BT_LOGI("format string", ...)+`:: Generic info logging statement. `+BT_LOGW("format string", ...)+`:: Generic warning logging statement. `+BT_LOGE("format string", ...)+`:: Generic error logging statement. `+BT_LOGF("format string", ...)+`:: Generic fatal logging statement. `+BT_LOGT_STR("preformatted string")+`:: Generic preformatted string trace logging statement. `+BT_LOGD_STR("preformatted string")+`:: Generic preformatted string debug logging statement. `+BT_LOGI_STR("preformatted string")+`:: Generic preformatted string info logging statement. `+BT_LOGW_STR("preformatted string")+`:: Generic preformatted string warning logging statement. `+BT_LOGE_STR("preformatted string")+`:: Generic preformatted string error logging statement. `+BT_LOGF_STR("preformatted string")+`:: Generic preformatted string fatal logging statement. `+BT_LOGT_MEM(data_ptr, data_size, "format string", ...)+`:: Generic memory trace logging statement. `+BT_LOGD_MEM(data_ptr, data_size, "format string", ...)+`:: Generic memory debug logging statement. `+BT_LOGI_MEM(data_ptr, data_size, "format string", ...)+`:: Generic memory info logging statement. `+BT_LOGW_MEM(data_ptr, data_size, "format string", ...)+`:: Generic memory warning logging statement. `+BT_LOGE_MEM(data_ptr, data_size, "format string", ...)+`:: Generic memory error logging statement. `+BT_LOGF_MEM(data_ptr, data_size, "format string", ...)+`:: Generic memory fatal logging statement. `+BT_LOGT_ERRNO("initial message", "format string", ...)+`:: Generic `errno` string trace logging statement. `+BT_LOGD_ERRNO("initial message", "format string", ...)+`:: Generic `errno` string debug logging statement. `+BT_LOGI_ERRNO("initial message", "format string", ...)+`:: Generic `errno` string info logging statement. `+BT_LOGW_ERRNO("initial message", "format string", ...)+`:: Generic `errno` string warning logging statement. `+BT_LOGE_ERRNO("initial message", "format string", ...)+`:: Generic `errno` string error logging statement. `+BT_LOGF_ERRNO("initial message", "format string", ...)+`:: Generic `errno` string fatal logging statement. [[lib-logging-statements]] ==== Library-specific logging statement macros The {bt2} library contains an internal logging API based on the generic logging framework. You can use it to log known {bt2} objects without having to manually log each member. See <> and <> to learn how to be able to use the following macros. The library logging statement macros are named `+BT_LIB_LOG*()+` instead of `+BT_LOG*()+`: `+BT_LIB_LOGT("format string", ...)+`:: Library trace logging statement. `+BT_LIB_LOGD("format string", ...)+`:: Library debug logging statement. `+BT_LIB_LOGI("format string", ...)+`:: Library info logging statement. `+BT_LIB_LOGW("format string", ...)+`:: Library warning logging statement. `+BT_LIB_LOGE("format string", ...)+`:: Library error logging statement. `+BT_LIB_LOGF("format string", ...)+`:: Library fatal logging statement. `+BT_LIB_LOGW_APPEND_CAUSE("format string", ...)+`:: Library warning logging statement, and unconditional error cause appending. `+BT_LIB_LOGE_APPEND_CAUSE("format string", ...)+`:: Library error logging statement, and unconditional error cause appending. `+BT_LIB_LOGF_APPEND_CAUSE("format string", ...)+`:: Library fatal logging statement, and unconditional error cause appending. The macros above accept the typical `printf()` conversion specifiers with the following limitations: * The `+*+` width specifier is not accepted. * The `+*+` precision specifier is not accepted. * The `j` and `t` length modifiers are not accepted. * The `n` format specifier is not accepted. * The format specifiers defined in `` are not accepted, except for `PRId64`, `PRIu64`, `PRIx64`, `PRIX64`, `PRIo64`, and `PRIi64`. The {bt2} library custom conversion specifier is accepted. Its syntax is either `%!u` to format a UUID (`bt_uuid` type), or: . Introductory `%!` sequence. . **Optional**: `[` followed by a custom prefix for the printed fields of this specifier, followed by `]`. The standard form is to end this prefix with `-` so that, for example, with the prefix `tc-`, the complete field name becomes `tc-addr`. . **Optional**: `pass:[+]` to print extended object members. This depends on the provided format specifier. . Format specifier (see below). The available format specifiers are: [options="header,autowidth",cols="3"] |=== |Specifier |Object |Expected C type |`F` |Trace IR field class |`+const struct bt_field_class *+` |`f` |Trace IR field |`+const struct bt_field *+` |`P` |Trace IR field path |`+const struct bt_field_path *+` |`E` |Trace IR event class |`+const struct bt_event_class *+` |`e` |Trace IR event |`+const struct bt_event *+` |`S` |Trace IR stream class. |`+const struct bt_stream_class *+` |`s` |Trace IR stream |`+const struct bt_stream *+` |`a` |Trace IR packet |`+const struct bt_packet *+` |`T` |Trace IR trace class |`+const struct bt_trace_class *+` |`t` |Trace IR trace |`+const struct bt_trace *+` |`K` |Trace IR clock class |`+const struct bt_clock_class *+` |`k` |Trace IR clock snapshot |`+const struct bt_clock_snapshot *+` |`v` |Value object |`+const struct bt_value *+` |`R` |Integer range set |`const struct bt_integer_range_set *` |`n` |Message |`+const struct bt_message *+` |`I` |Message iterator class |`struct bt_message_iterator_class *` |`i` |Message iterator |`struct bt_message_iterator *` |`C` |Component class |`struct bt_component_class *` |`c` |Component |`+const struct bt_component *+` |`p` |Port |`+const struct bt_port *+` |`x` |Connection |`+const struct bt_connection *+` |`g` |Graph |`+const struct bt_graph *+` |`z` |Interrupter |`+struct bt_interrupter *+` |`l` |Plugin |`+const struct bt_plugin *+` |`r` |Error cause |`+const struct bt_error_cause *+` |`o` |Object pool |`+const struct bt_object_pool *+` |`O` |Object |`+const struct bt_object *+` |=== Conversion specifier examples: * `%!f` * `%![my-event-]+e` * `%!t` * `%!+F` The ``, `` string (comma and space) is printed between individual fields, but **not after the last one**. Therefore, you must put this separator in the format string between two conversion specifiers, for example: [source,c] ---- BT_LIB_LOGW("Message: count=%u, %!E, %!+K", count, event_class, clock_class); ---- Example with a custom prefix: [source,c] ---- BT_LIB_LOGI("Some message: %![ec-a-]e, %![ec-b-]+e", ec_a, ec_b); ---- It is safe to pass `NULL` as any {bt2} object parameter: the macros only print its null address. WARNING: Build-time `printf()` format checks are disabled for the `+BT_LIB_LOG*()+` macros because there are custom conversion specifiers, so make sure to test your logging statements. [[comp-logging-statements]] ==== Component-specific logging statement macros There are available logging macros for components. They prepend a prefix including the component's name to the logging message. See <> and <> to learn how to be able to use the following macros. The component logging statement macros are named `+BT_COMP_LOG*()+` instead of `+BT_LOG*()+`: `+BT_COMP_LOGT("format string", ...)+`:: Component trace logging statement. `+BT_COMP_LOGD("format string", ...)+`:: Component debug logging statement. `+BT_COMP_LOGI("format string", ...)+`:: Component info logging statement. `+BT_COMP_LOGW("format string", ...)+`:: Component warning logging statement. `+BT_COMP_LOGE("format string", ...)+`:: Component error logging statement. `+BT_COMP_LOGF("format string", ...)+`:: Component fatal logging statement. `+BT_COMP_LOGT_STR("preformatted string")+`:: Component preformatted string trace logging statement. `+BT_COMP_LOGD_STR("preformatted string")+`:: Component preformatted string debug logging statement. `+BT_COMP_LOGI_STR("preformatted string")+`:: Component preformatted string info logging statement. `+BT_COMP_LOGW_STR("preformatted string")+`:: Component preformatted string warning logging statement. `+BT_COMP_LOGE_STR("preformatted string")+`:: Component preformatted string error logging statement. `+BT_COMP_LOGF_STR("preformatted string")+`:: Component preformatted string fatal logging statement. `+BT_COMP_LOGT_ERRNO("initial message", "format string", ...)+`:: Component `errno` string trace logging statement. `+BT_COMP_LOGD_ERRNO("initial message", "format string", ...)+`:: Component `errno` string debug logging statement. `+BT_COMP_LOGI_ERRNO("initial message", "format string", ...)+`:: Component `errno` string info logging statement. `+BT_COMP_LOGW_ERRNO("initial message", "format string", ...)+`:: Component `errno` string warning logging statement. `+BT_COMP_LOGE_ERRNO("initial message", "format string", ...)+`:: Component `errno` string error logging statement. `+BT_COMP_LOGF_ERRNO("initial message", "format string", ...)+`:: Component `errno` string fatal logging statement. `+BT_COMP_LOGT_MEM(data_ptr, data_size, "format string", ...)+`:: Component memory trace logging statement. `+BT_COMP_LOGD_MEM(data_ptr, data_size, "format string", ...)+`:: Component memory debug logging statement. `+BT_COMP_LOGI_MEM(data_ptr, data_size, "format string", ...)+`:: Component memory info logging statement. `+BT_COMP_LOGW_MEM(data_ptr, data_size, "format string", ...)+`:: Component memory warning logging statement. `+BT_COMP_LOGE_MEM(data_ptr, data_size, "format string", ...)+`:: Component memory error logging statement. `+BT_COMP_LOGF_MEM(data_ptr, data_size, "format string", ...)+`:: Component memory fatal logging statement. ==== Conditional logging `+BT_LOG_IF(cond, statement)+`:: Execute `statement` only if `cond` is true. + Example: + -- [source,c] ---- BT_LOG_IF(i < count / 2, BT_LOGD("Log this: i=%d", i)); ---- -- To check the <>: [source,c] ---- #if BT_LOG_ENABLED_DEBUG ... #endif ---- This tests if the _DEBUG_ level was enabled at build time. This means that the current, <> _could_ be _DEBUG_, but it could also be higher. The rule of thumb is to use only logging statements at the same level in a `BT_LOG_ENABLED_*` conditional block. The available definitions for build-time conditions are: * `BT_LOG_ENABLED_TRACE` * `BT_LOG_ENABLED_DEBUG` * `BT_LOG_ENABLED_INFO` * `BT_LOG_ENABLED_WARNING` * `BT_LOG_ENABLED_ERROR` * `BT_LOG_ENABLED_FATAL` To check the current, <>: [source,c] ---- if (BT_LOG_ON_DEBUG) { ... } ---- This tests if the _DEBUG_ log level is dynamically turned on (implies that it's also enabled at build time). This check could have a noticeable impact on performance. The available definitions for run-time conditions are: * `BT_LOG_ON_TRACE` * `BT_LOG_ON_DEBUG` * `BT_LOG_ON_INFO` * `BT_LOG_ON_WARNING` * `BT_LOG_ON_ERROR` * `BT_LOG_ON_FATAL` Those macros check the module-specific log level symbol (defined by `BT_LOG_OUTPUT_LEVEL`). Never, ever write code which would be executed only to compute the fields of a logging statement outside a conditional logging scope, for example: [source,c] ---- int number = get_number_of_event_classes_with_property_x(...); BT_LOGD("Bla bla: number=%d", number); ---- Do this instead: [source,c] ---- if (BT_LOG_ON_DEBUG) { int number = get_number_of_event_classes_with_property_x(...); BT_LOGD("Bla bla: number=%d", number); } ---- Or even this: [source,c] ---- BT_LOGD("Bla bla: number=%d", get_number_of_event_classes_with_property_x(...)); ---- === Guides [[logging-instrument-c-file-gen]] ==== Instrument a {c-cpp} source file (generic) To instrument a {c-cpp} source file (`.c`/`.cpp`): . At the top of the file, before the first `#include` line (if any), define your file's <> name: + -- [source,c] ---- #define BT_LOG_TAG "SUBSYS/MY-MODULE/MY-FILE" ---- -- . Below the line above, define the source file's log level expression, `BT_LOG_OUTPUT_LEVEL`. This expression is evaluated for each <> to know the current <>. + Examples: + [source,c] ---- /* Global log level variable */ #define BT_LOG_OUTPUT_LEVEL module_global_log_level ---- + [source,c] ---- /* Local log level variable; must exist where you use BT_LOG*() */ #define BT_LOG_OUTPUT_LEVEL log_level ---- + [source,c] ---- /* Object's log level; `obj` must exist where you use BT_LOG*() */ #define BT_LOG_OUTPUT_LEVEL (obj->log_level) ---- . Include `"logging/log.h"`: + [source,c] ---- #include "logging/log.h" ---- . In the file, instrument your code with the <>. [[logging-instrument-h-file-gen]] ==== Instrument a {c-cpp} header file (generic) To instrument a {c-cpp} header file (`.h`/`.hpp`), if you have `static inline` functions in it: . Do not include `"logging/log.h"`! . Do one of: .. In the file, instrument your code with the <>, making each of them conditional to the existence of the macro you're using: + [source,c] ---- static inline int some_function(int x) { /* ... */ #ifdef BT_LOGT BT_LOGT(...); #endif /* ... */ #ifdef BT_LOGW_STR BT_LOGW_STR(...); #endif /* ... */ } ---- + The {c-cpp} source files which include this header file determine if logging is enabled or not for them, and if so, what is their <> and <> expression. .. Require that logging be enabled: + [source,c] ---- /* Protection: this file uses BT_LOG*() macros directly */ #ifndef BT_LOG_SUPPORTED # error Please include "logging/log.h" before including this file. #endif ---- + Then, in the file, instrument your code with the <>. [[logging-instrument-c-file-lib]] ==== Instrument a library {c-cpp} source file To instrument a library {c-cpp} source file (`.c`/`.cpp`): . At the top of the file, before the first `#include` line (if any), define your file's <> name (this tag must start with `LIB/`): + -- [source,c] ---- #define BT_LOG_TAG "LIB/THE-FILE" ---- -- . Include `"lib/logging.h"`: + [source,c] ---- #include "lib/logging.h" ---- . In the file, instrument your code with the <> or with the <>. [[logging-instrument-h-file-lib]] ==== Instrument a library {c-cpp} header file To instrument a library {c-cpp} header file (`.h`/`.hpp`), if you have `static inline` functions in it: . Do not include `"lib/logging.h"`! . Require that library logging be enabled: + [source,c] ---- /* Protection: this file uses BT_LIB_LOG*() macros directly */ #ifndef BT_LIB_LOG_SUPPORTED # error Please include "lib/logging.h" before including this file. #endif ---- . In the file, instrument your code with the <> or with the <>. [[logging-instrument-c-file-compcls]] ==== Instrument a component class {c-cpp} source file To instrument a component class {c-cpp} source file (`.c`/`.cpp`): . At the top of the file, before the first `#include` line (if any), define your file's <> name (this tag must start with `PLUGIN/` followed by the component class identifier): + -- [source,c] ---- #define BT_LOG_TAG "PLUGIN/SRC.MY-PLUGIN.MY-SRC" ---- -- . Below the line above, define the source file's log level expression, `BT_LOG_OUTPUT_LEVEL`. This expression is evaluated for each <> to know the current <>. + For a component class file, it is usually a member of a local component private structure variable: + [source,c] ---- #define BT_LOG_OUTPUT_LEVEL (my_comp->log_level) ---- . Below the line above, define `BT_COMP_LOG_SELF_COMP` to an expression which, evaluated in the context of the <>, evaluates to the self component address (`+bt_self_component *+`) of the component. + This is usually a member of a local component private structure variable: + [source,c] ---- #define BT_COMP_LOG_SELF_COMP (my_comp->self_comp) ---- . Include `"logging/comp-logging.h"`: + [source,c] ---- #include "logging/comp-logging.h" ---- . In the component initialization method, make sure to set the component private structure's log level member to the initial component's log level: + [source,c] ---- struct my_comp { bt_logging_level log_level; /* ... */ }; BT_HIDDEN bt_self_component_status my_comp_init( bt_self_component_source *self_comp_src, bt_value *params, void *init_method_data) { struct my_comp *my_comp = g_new0(struct my_comp, 1); bt_self_component *self_comp = bt_self_component_source_as_self_component(self_comp_src); const bt_component *comp = bt_self_component_as_component(self_comp); BT_ASSERT(my_comp); my_comp->log_level = bt_component_get_logging_level(comp); /* ... */ } ---- . In the file, instrument your code with the <>. [[logging-instrument-h-file-compcls]] ==== Instrument a component class {c-cpp} header file To instrument a component class {c-cpp} header file (`.h`/`.hpp`), if you have `static inline` functions in it: . Do not include `"logging/comp-logging.h"`! . Require that component logging be enabled: + [source,c] ---- /* Protection: this file uses BT_COMP_LOG*() macros directly */ #ifndef BT_COMP_LOG_SUPPORTED # error Please include "logging/comp-logging.h" before including this file. #endif ---- . In the file, instrument your code with the <>. [[choose-a-logging-tag]] ==== Choose a logging tag Each logging-enabled {c-cpp} source file must define `BT_LOG_TAG` to a logging tag. A logging tag is a namespace to identify the logging messages of this specific source file. In general, a logging tag name _must_ be only uppercase letters, digits, and the `-`, `.`, and `/` characters. Use `/` to show the subsystem to source file hierarchy. For the {bt2} library, start with `LIB/`. For the CTF writer library, start with `CTF-WRITER/`. For component classes, use: [verse] `PLUGIN/__CCTYPE__.__PNAME__.__CCNAME__[/__FILE__]` With: `__CCTYPE__`:: Component class's type (`SRC`, `FLT`, or `SINK`). `__PNAME__`:: Plugin's name. `__CCNAME__`:: Component class's name. `__FILE__`:: Additional information to specify the source file name or module. For plugins (files common to many component classes), use: [verse] `PLUGIN/__PNAME__[/__FILE__]` With: `__PNAME__`:: Plugin's name. `__FILE__`:: Additional information to specify the source file name or module. [[choose-a-log-level]] ==== Choose a log level Choosing the appropriate level for your logging statement is very important. [options="header,autowidth",cols="1,2,3a,4"] |=== |Log level |Description |Use cases |Expected impact on performance |_FATAL_ | The program, library, or plugin cannot continue to work in this condition: it must be terminated immediately. A _FATAL_-level logging statement should always be followed by `abort()`. | * Unexpected return values from system calls. * Logic error in internal code, for example an unexpected value in a `switch` statement. * Failed assertion (within `BT_ASSERT()`). * Unsatisfied library precondition (within `BT_ASSERT_PRE()` or `BT_ASSERT_PRE_DEV()`). * Unsatisfied library postcondition (within `BT_ASSERT_POST()` or `BT_ASSERT_POST_DEV()`). |Almost none: always enabled. |_ERROR_ | An important error which is somewhat not fatal, that is, the program, library, or plugin can continue to work after this, but you judge that it should be reported to the user. Usually, the program cannot recover from such an error, but it can at least exit cleanly. | * Memory allocation errors. * Wrong component initialization parameters. * Corrupted, unrecoverable trace data. * Failed to perform an operation which should work considering the implementation and the satisfied preconditions. For example, the failure to create an empty object (no parameters): most probably failed internally because of an allocation error. * Almost any error in terminal elements: CLI and plugins. |Almost none: always enabled. |_WARNING_ | An error which still allows the execution to continue, but you judge that it should be reported to the user. _WARNING_-level logging statements are for any error or weird action that is directly or indirectly caused by the user, often through some bad input data. For example, not having enough memory is considered beyond the user's control, so we always log memory errors with an _ERROR_ level (not _FATAL_ because we usually don't abort in this condition). | * Missing data within something that is expected to have it, but there's an alternative. * Invalid file, but recoverable/fixable. |Almost none: always enabled. |_INFO_ | Any useful information which a non-developer user would possibly understand. Anything logged with this level must _not_ happen repetitively on the fast path, that is, nothing related to each message, for example. This level is used for sporadic and one-shot events. | * CLI or component configuration report. * Successful plugin, component, or message iterator initialization. * In the library: anything related to plugins, graphs, component classes, components, message iterators, connections, and ports which is not on the fast path. * Successful connection to or disconnection from another system. * An _optional_ subsystem cannot be loaded. * An _optional_ field/datum cannot be found. | Very little: always enabled. |_DEBUG_ | Something that only {bt2} developers would be interested into, which can occur on the fast path, but not more often than once per message. The _DEBUG_ level is the default <> as, since it's not _too_ verbose, the performance is similar to an _INFO_ build. | * Object construction and destruction. * Object recycling (except fields). * Object copying (except fields and values). * Object freezing (whatever the type, as freezing only occurs in developer mode). * Object interruption. * Calling user methods and logging the result. * Setting object properties (except fields and values). | Noticeable, but not as much as the _TRACE_ level: could be executed in production if you're going to need a thorough log for support tickets without having to rebuild the project. |_TRACE_ | Low-level debugging context information (anything that does not fit the other log levels). More appropriate for tracing in general. | * Reference count change. * Fast path, low level state machine's state change. * Get or set an object's property. * Object comparison's intermediate results. |Huge: not executed in production. |=== [IMPORTANT] -- Make sure not to use a _WARNING_ (or higher) log level when the condition leading to the logging statement can occur under normal circumstances. For example, a public function to get some object or property from an object by name or key that fails to find the value is not a warning scenario: the user could legitimately use this function to check if the name/key exists in the object. In this case, use the _TRACE_ level (or do not log at all). -- [[message]] ==== Write an appropriate message Follow those rules when you write a logging statement's message: * Use an English sentence which starts with a capital letter. * Start the sentence with the appropriate verb tense depending on the context. For example: + -- ** Beginning of operation (present continuous): _Creating ..._, _Copying ..._, _Serializing ..._, _Freezing ..._, _Destroying ..._ ** End of operation (simple past): _Created ..._, _Successfully created ..._, _Failed to create ..._, _Set ..._ (simple past of _to set_ which is also _set_) -- + For warning and error messages, you can start the message with _Cannot_ or _Failed to_ followed by a verb if it's appropriate. * Do not include the log level in the message itself. For example, do not start the message with _Error while_ or _Warning:_. * Do not put newlines, tabs, or other special characters in the message, unless you want to log a string with such characters. Note that multiline logging messages can be hard to parse, analyze, and filter, however, so prefer multiple logging statements over a single statement with newlines. * **If there are fields that your logging statement must record**, follow the message with `:` followed by a space, then with the list of fields (more about this below). If there are no fields, end the sentence with a period. The statement's fields _must_ be a comma-separated list of `__name__=__value__` tokens. Keep `__name__` as simple as possible; use kebab case if possible. If `__value__` is a non-alphanumeric string, put it between double quotes (`"%s"` specifier). Always use the `PRId64` and `PRIu64` specifiers to log an `int64_t` or an `uint64_t` value. Use `%d` to log a boolean value. Example: "Cannot read stream data for indexing: path=\"%s\", name=\"%s\", " "stream-id=%" PRIu64 ", stream-fd=%d, " "index=%" PRIu64 ", status=%s, is-mapped=%d" By following a standard format for the statement fields, it is easier to use tools like https://www.elastic.co/products/logstash[Logstash] or even https://www.splunk.com/[Splunk] to split fields and analyze logs. Prefer the following suffixes in field names: [options="header,autowidth"] |=== |Field name suffix |Description |Format specifier |`-addr` |Memory address |`%p` |`-fd` |File descriptor |`%d` |`-fp` |File stream (`+FILE *+`) |`%p` |`-id` |Object's ID |`%" PRIu64 "` |`-index` |Index |`%" PRIu64 "` |`-name` |Object's name |`\"%s\"` |=== === Output The log is printed to the standard error stream. A log line contains the time, the process and thread IDs, the <>, the <>, the source's function name, file name and line number, and the <>. When {bt2} supports terminal color codes (depends on the `BABELTRACE_TERM_COLOR` environment variable's value and what the standard output and error streams are plugged into), _INFO_-level lines are blue, _WARNING_-level lines are yellow, and _ERROR_-level and _FATAL_-level lines are red. Log line example: ---- 05-11 00:58:03.691 23402 23402 D VALUES bt_value_destroy@values.c:498 Destroying value: addr=0xb9c3eb0 ---- You can easily filter the log with `grep` or `ag`. For example, to keep only the _DEBUG_-level logging messages that the `FIELD-CLASS` module generates: ---- $ babeltrace2 --log-level=D /path/to/trace |& ag 'D FIELD-CLASS' ---- == Valgrind To use Valgrind on an application (for example, the CLI or a test) which loads libbabeltrace2, use: ---- $ G_SLICE=always-malloc G_DEBUG=gc-friendly PYTHONMALLOC=malloc \ LIBBABELTRACE2_NO_DLCLOSE=1 valgrind --leak-check=full app ---- `G_SLICE=always-malloc` and `G_DEBUG=gc-friendly` is for GLib and `PYTHONMALLOC=malloc` is for the Python interpreter, if it is used by the Python plugin provider (Valgrind will probably show a lot of errors which originate from the Python interpreter anyway). `LIBBABELTRACE2_NO_DLCLOSE=1` makes libbabeltrace2 not close the shared libraries (plugins) which it loads. You need this to see the appropriate backtrace when Valgrind shows errors. == Testing [[test-env]] === Environment `tests/utils/utils.sh` sets the environment variables for any {bt2} test script. `utils.sh` only needs to know the path to the `tests` directory within the source and the build directories. By default, `utils.sh` assumes the build is in tree, that is, you ran `./configure` from the source's root directory, and sets the `BT_TESTS_SRCDIR` and `BT_TESTS_BUILDDIR` environment variables accordingly. You can override those variables, for example if you build out of tree. All test scripts eventually do something like this to source `utils.sh`, according to where they are located relative to the `tests` directory: [source,bash] ---- if [ "x${BT_TESTS_SRCDIR:-}" != "x" ]; then UTILSSH="$BT_TESTS_SRCDIR/utils/utils.sh" else UTILSSH="$(dirname "$0")/../utils/utils.sh" fi ---- ==== Python You can use the `tests/utils/run_python_bt2` script to run any command within an environment making the build's `bt2` Python package available. `run_python_bt2` uses <> which needs to know the build directory, so make sure you set the `BT_TESTS_BUILDDIR` environment variable correctly _if you build out of tree_, for example: ---- $ export BT_TESTS_BUILDDIR=/path/to/build/babeltrace/tests ---- You can run any command which needs the `bt2` Python package through `run_python_bt2`, for example: ---- $ ./tests/utils/run_python_bt2 ipython3 ---- === Report format All test scripts output the test results following the https://testanything.org/[Test Anything Protocol] (TAP) format. The TAP format has two mechanisms to print additional information about a test: * Print a line starting with `#` to the standard output. + This is usually done with the `diag()` C function or the `diag` shell function. * Print to the standard error. === Python bindings The `bt2` Python package tests are located in `tests/bindings/python/bt2`. ==== Python test runner `tests/utils/python/testrunner.py` is {bt2}'s Python test runner which loads Python files containing unit tests, finds all the test cases, and runs the tests, producing a TAP report. You can see the test runner command's help with: ---- $ python3 ./tests/utils/python/testrunner.py --help ---- By default, the test runner reports failing tests (TAP's `not{nbsp}ok` line), but continues to run other tests. You can use the `--failfast` option to make the test runner fail as soon as a test fails. ==== Guides To run all the `bt2` Python package tests: * Run: + ---- $ ./tests/utils/run_python_bt2 ./tests/bindings/python/bt2/test_python_bt2 ---- + or: + ---- $ ./tests/utils/run_python_bt2 python3 ./tests/utils/python/testrunner.py \ ./tests/bindings/python/bt2/ -p '*.py' ---- To run **all the tests** in a test module (for example, `test_value.py`): * Run: + ---- $ ./tests/utils/run_python_bt2 python3 ./tests/utils/python/testrunner.py \ ./tests/bindings/python/bt2 -t test_value ---- To run a **specific test case** (for example, `RealValueTestCase` within `test_value.py`): * Run: + ---- $ ./tests/utils/run_python_bt2 python3 ./tests/utils/python/testrunner.py \ ./tests/bindings/python/bt2/ -t test_value.RealValueTestCase ---- To run a **specific test** (for example, `RealValueTestCase.test_assign_pos_int` within `test_value.py`): * Run: + ---- $ ./tests/utils/run_python_bt2 python3 ./tests/utils/python/testrunner.py \ ./tests/bindings/python/bt2/ -t test_value.RealValueTestCase.test_assign_pos_int ---- == {cpp} usage Some parts of {bt2} are written in {cpp}. This section shows what's important to know about {cpp} to contribute to {bt2}. [IMPORTANT] ==== {bt2} only has {cpp} sources for _internal_ code. In other words, libbabeltrace2 _must_ expose a pure C99 API to preserve ABI compatibility over time. ==== === Standard and dependencies The {bt2} project is configured to use the {cpp11} standard. {cpp11} makes it possible to build {bt2} with a broad range of compilers, from GCC{nbsp}4.8 and Clang{nbsp}3.3. === Automake/Libtool requirements To add a {cpp} source file to a part of the project, use the `.cpp` extension and add it to the list of source files in `Makefile.am` as usual. If a program or a shared library has a direct {cpp} source file, then Libtool uses the {cpp} linker to create the result, dynamically linking important runtime libraries such as libstdc++ and libgcc_s. Because a Libtool _convenience library_ is just an archive (`.a`), it's _not_ dynamically linked to runtime libraries, even if one of its direct sources is a {cpp} file. This means that for each program or shared library named `my_target` in `Makefile.am` which is linked to a convenience library having {cpp} sources (recursively), you _must_ do one of: * Have at least one direct {cpp} source file in the `+*_my_target_SOURCES+` list. * Add: + ---- nodist_EXTRA_my_target_SOURCES = dummy.cpp ---- + See https://www.gnu.org/software/automake/manual/automake.html#Libtool-Convenience-Libraries[Libtool Convenience Libraries] to learn more. For a given program or library, you _cannot_ have a C{nbsp}file and a {cpp}{nbsp}file having the same name, for example `list.c` and `list.cpp`. === Coding style ==== Whitespaces, indentation, and line breaks All the project's {cpp} files follow the https://clang.llvm.org/docs/ClangFormat.html[clang-format] https://clang.llvm.org/docs/ClangFormatStyleOptions.html[style] of the `.clang-format` file for whitespaces, indentation, and line breaks. You _must_ format modified and new {cpp} files with clang-format before you create a contribution patch. You need clang-format{nbsp}≥{nbsp}10 to use the project's `.clang-format` file. To automatically format all the project's {cpp} files, run: ---- $ ./tools/format-cpp ---- Use the `FORMATTER` environment variable to override the default formatter (`clang-format{nbsp}-i`): ---- $ FORMATTER='clang-format-10 -i' ./tools/format-cpp ---- ==== Naming * Use camel case with a lowercase first letter for: ** Variable names: `size`, `objSize`. ** Function/method names: `size()`, `formatAndPrint()`. * Use camel case with an uppercase first letter for: ** Types: `Pistachio`, `NutManager`. ** Template parameters: `PlanetT`, `TotalSize`. * Use snake case with uppercase letters for: ** Definition/macro names: `MARK_AS_UNUSED()`, `SOME_FEATURE_EXISTS`. ** Enumerators: `Type::SIGNED_INT`, `Scope::FUNCTION`. * Use only lowercase letters and digits for namespaces: `mylib`, `bt2`. * Use the suffix `T` for type template parameters: + [source,cpp] ---- template ---- * Name a template parameter pack `Args`. + [source,cpp] ---- template ---- * Use an underscore prefix for private and protected methods and member type names: `_tryConnect()`, `_NodeType`. * Use the prefix `_m` for private and protected member variable names: `_mLogger`, `_mSize`, `_mFieldClass`. * Name setters and getters like the property name, without `set` and `get` prefixes. * Use the `is` or `has` prefix, if possible, to name the functions which return `bool`. === Coding convention In general, the project's contributors make an effort to follow, for {cpp11} code: * The https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md[{cpp} Core Guidelines]. * Scott Meyers's "`https://www.oreilly.com/library/view/effective-modern-c/9781491908419/[Effective Modern {cpp}]`". Here are a few important reminders: * Namespace your code. * Create one header/source file pair per class when possible. + For a class named `MyClass`, name the corresponding files `my-class.hpp` and `my-class.cpp`. * When defining a class, put constructors as the first methods, whatever their access (public/protected/private), then the destructor, and then the rest. * Declare variables as close to where they are used as possible. * Use `auto` when possible. * Use `const` as much as possible, even for pointer (`+const char* const+`) and numeric values (`const unsigned int`) which never need to change. * Implement simple setters, getters, and one-liners in header files and everything else that's not a template in source files. * Make methods `const noexcept` or `const` as much as possible. * Make constructors `explicit` unless you really need an implicit constructor (which is rare). * Use `std::unique_ptr` to manage memory when possible. + However, use references (`+*my_unique_ptr+`) and raw pointers (`+my_unique_ptr.get()+`) when not transferring ownership. * Use `nullptr`, not `NULL` nor 0. * Return by value (rvalue) instead of by output parameter (non-const lvalue reference), even complex objects, unless you can prove that the performance is improved when returning by parameter. * For a function parameter or a return value of which the type needs to be a reference or pointer, use: + If the value is mandatory::: A reference. If the value is optional::: A raw pointer. * Don't use `+std::move()+` when you already have an rvalue, which means: ** Don't write `+return std::move(...);+` as this can interfere with RVO. ** Don't use `+std::move()+` with a function call (`+std::move(func())+`). * For each possible move/copy constructor or assignment operator, do one of: ** Write a custom one. ** Mark it as defaulted (`default`) ** Mark it as deleted (`delete`). * Use scoped enumerations (`+enum class+`). * Mark classes known to be final with the `final` keyword. * Use type aliases (`using`), not type definitions (`typedef`). * Use anonymous namespaces for local functions instead of `static`. * Don't pollute the global namespace: ** Don't use `using namespace xyz` anywhere. ** Use only namespace aliases in source files (`.cpp`), trying to use them in the smallest possible scope (function, or even smaller). * Return a structure with named members instead of a generic container such as `std::pair` or `std::tuple`. * When a class inherits a base class with virtual methods, use the `override` keyword to mark overridden virtual methods, and do not use the `virtual` keyword again. * Define overloaded operators only if their meaning is obvious, unsurprising, and consistent with the corresponding built-in operators. + For example, use `+|+` as a bitwise- or logical-or, not as a shell-style pipe. * Use RAII wrappers when managing system resources or interacting with C{nbsp}libraries. + In other words, don't rely on ``goto``s and error labels to clean up as you would do in{nbsp}C. + Use the RAII, Luke. * Throw an exception when there's an unexpected, exceptional condition, https://isocpp.org/wiki/faq/exceptions#ctors-can-throw[including from a constructor], instead of returning a status code. * Accept a by-value parameter and move it (when it's moveable) when you intend to copy it anyway. + You can do this with most STL containers. + Example: + [source,cpp] ---- void Obj::doSomething(std::string str) { _mName = std::move(str); // ... } ---- .`baby.hpp` ==== This example shows a {cpp} header which follows the {bt2} {cpp} coding convention. [source,cpp] ---- /* * SPDX-License-Identifier: MIT * * Copyright 2020 Harry Burnett */ #ifndef BABELTRACE_BABY_HPP #define BABELTRACE_BABY_HPP #include #include #include namespace life { class Toy; /* * A baby is a little human. */ class Baby : public Human { public: using Toys = std::unordered_set; enum class Gender { MALE, FEMALE, UNKNOWN, }; Baby() = default; explicit Baby(const Toys& toys); Baby(const Baby&) = delete; Baby(Baby&&) = delete; Baby& operator=(const Baby&) = delete; Baby& operator=(Baby&&) = delete; protected: explicit Baby(Gender initialGender = Gender::UNKNOWN); public: /* * Eats `weight` grams of food. */ void eat(unsigned long weight); /* * Sleeps for `duration` seconds. */ void sleep(double duration); /* * Sets this baby's name to `name`. */ void name(std::string name) { _mName = std::move(name); } /* * This baby's name. */ const std::string& name() const noexcept { return _mName; } protected: void _addTeeth(unsigned long index); void _grow(double size) override; private: std::string _mName {"Paul"}; Toys _mToys; }; } // namespace life #endif // BABELTRACE_BABY_HPP ---- ====