From 72384ba31a5433c15d67313b339556239bf0c316 Mon Sep 17 00:00:00 2001 From: "Paul N. Hilfinger" Date: Wed, 11 Jan 2012 10:34:21 +0000 Subject: [PATCH] Have block_innermost_frame start from selected frame and document. GDB used to search for the frame containing variables in a particular lexical block starting from the current (top) frame, ignoring any currently selected frame. It is not clear why this is desirable for variables that require a frame; why would a user deliberately select one frame and then expect to see the value of a variable in a more recent frame? This change causes block_innermost_frame to start looking from the selected frame, if there is one. It may be unnecessarily conservative: we use get_selected_frame_if_set rather than get_selected_frame in order to avoid the side effect of calling select_frame, which would probably be harmless. Expression-parsing routines previously made the unwarranted assumption that all block-qualified variables (written with the GDB extension ::) are static. As a result, they failed to update innermost_block, which confused the watch commands about when variables in watched expressions went out of scope, and also caused the wrong variables to be watched. This patch also modifies these routines to treat all local variables the same whether or not they are block-qualified. Finally, we add a paragraph to the "Program Variables" section of the texinfo documentation concerning the use of "::" for accessing non-static variables. 2012-01-11 Paul Hilfinger * gdb/blockframe.c (block_innermost_frame): Start search from selected frame, if present, or otherwise the current frame. * gdb/c-exp.y (variable): Update innermost_block for 'block COLONCOLON NAME' clause. * gdb/m2-exp.y (variable): Ditto. * gdb/objc-exp.y (variable): Ditto. * gdb/doc/gdb.texinfo (Variables): Document use of :: for non-static variables. --- gdb/ChangeLog | 10 ++++++++++ gdb/blockframe.c | 9 ++++++--- gdb/c-exp.y | 7 +++++++ gdb/doc/ChangeLog | 5 +++++ gdb/doc/gdb.texinfo | 45 +++++++++++++++++++++++++++++++++++++++++++-- gdb/m2-exp.y | 7 +++++++ gdb/objc-exp.y | 7 +++++++ 7 files changed, 85 insertions(+), 5 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 1ac251038b..29f2d1e652 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,13 @@ +2012-01-11 Paul Hilfinger + + * blockframe.c (block_innermost_frame): Start search from selected + frame, if present, or otherwise the current frame. + + * c-exp.y (variable): Update innermost_block for + 'block COLONCOLON NAME' clause. + * m2-exp.y (variable): Ditto. + * objc-exp.y (variable): Ditto. + 2012-01-10 Tom Tromey PR python/13199: diff --git a/gdb/blockframe.c b/gdb/blockframe.c index 38973667cd..cb61cf30c5 100644 --- a/gdb/blockframe.c +++ b/gdb/blockframe.c @@ -352,8 +352,9 @@ find_pc_partial_function (CORE_ADDR pc, char **name, CORE_ADDR *address, return find_pc_partial_function_gnu_ifunc (pc, name, address, endaddr, NULL); } -/* Return the innermost stack frame executing inside of BLOCK, or NULL - if there is no such frame. If BLOCK is NULL, just return NULL. */ +/* Return the innermost stack frame that is executing inside of BLOCK and is + at least as old as the selected frame. Return NULL if there is no + such frame. If BLOCK is NULL, just return NULL. */ struct frame_info * block_innermost_frame (const struct block *block) @@ -368,7 +369,9 @@ block_innermost_frame (const struct block *block) start = BLOCK_START (block); end = BLOCK_END (block); - frame = get_current_frame (); + frame = get_selected_frame_if_set (); + if (frame == NULL) + frame = get_current_frame (); while (frame != NULL) { struct block *frame_block = get_frame_block (frame, NULL); diff --git a/gdb/c-exp.y b/gdb/c-exp.y index 24a47616e2..bf4f4bc1a7 100644 --- a/gdb/c-exp.y +++ b/gdb/c-exp.y @@ -778,6 +778,13 @@ variable: block COLONCOLON name if (sym == 0) error (_("No symbol \"%s\" in specified context."), copy_name ($3)); + if (symbol_read_needs_frame (sym)) + { + if (innermost_block == 0 + || contained_in (block_found, + innermost_block)) + innermost_block = block_found; + } write_exp_elt_opcode (OP_VAR_VALUE); /* block_found is set by lookup_symbol. */ diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index 5a9d2ff9df..2914190f9f 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,8 @@ +2012-01-11 Paul Hilfinger + + * gdb.texinfo (Variables): Document use of :: for non-static + variables. + 2012-01-05 Joel Brobecker * gdbint.texinfo (Start of New Year Procedure): Update diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 2f4aa4f25f..4a8ff7b97b 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -7306,7 +7306,7 @@ scope is a single source file even if the current execution point is not in this file. But it is possible to have more than one such variable or function with the same name (in different source files). If that happens, referring to that name has unpredictable effects. If you wish, -you can specify a static variable in a particular function or file, +you can specify a static variable in a particular function or file by using the colon-colon (@code{::}) notation: @cindex colon-colon, context for variables/functions @@ -7329,8 +7329,49 @@ to print a global value of @code{x} defined in @file{f2.c}: (@value{GDBP}) p 'f2.c'::x @end smallexample +The @code{::} notation is normally used for referring to +static variables, since you typically disambiguate uses of local variables +in functions by selecting the appropriate frame and using the +simple name of the variable. However, you may also use this notation +to refer to local variables in frames enclosing the selected frame: + +@smallexample +void +foo (int a) +@{ + if (a < 10) + bar (a); + else + process (a); /* Stop here */ +@} + +int +bar (int a) +@{ + foo (a + 5); +@} +@end smallexample + +@noindent +For example, if there is a breakpoint at the commented line, +here is what you might see +when the program stops after executing the call @code{bar(0)}: + +@smallexample +(@value{GDBP}) p a +$1 = 10 +(@value{GDBP}) p bar::a +$2 = 5 +(@value{GDBP}) up 2 +#2 0x080483d0 in foo (a=5) at foobar.c:12 +(@value{GDBP}) p a +$3 = 5 +(@value{GDBP}) p bar::a +$4 = 0 +@end smallexample + @cindex C@t{++} scope resolution -This use of @samp{::} is very rarely in conflict with the very similar +These uses of @samp{::} are very rarely in conflict with the very similar use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++} scope resolution operator in @value{GDBN} expressions. @c FIXME: Um, so what happens in one of those rare cases where it's in diff --git a/gdb/m2-exp.y b/gdb/m2-exp.y index 1e3e3cbcab..ef9ec8e9ea 100644 --- a/gdb/m2-exp.y +++ b/gdb/m2-exp.y @@ -588,6 +588,13 @@ variable: block COLONCOLON NAME if (sym == 0) error (_("No symbol \"%s\" in specified context."), copy_name ($3)); + if (symbol_read_needs_frame (sym)) + { + if (innermost_block == 0 + || contained_in (block_found, + innermost_block)) + innermost_block = block_found; + } write_exp_elt_opcode (OP_VAR_VALUE); /* block_found is set by lookup_symbol. */ diff --git a/gdb/objc-exp.y b/gdb/objc-exp.y index 346b404181..b43ba666d9 100644 --- a/gdb/objc-exp.y +++ b/gdb/objc-exp.y @@ -648,6 +648,13 @@ variable: block COLONCOLON name if (sym == 0) error (_("No symbol \"%s\" in specified context."), copy_name ($3)); + if (symbol_read_needs_frame (sym)) + { + if (innermost_block == 0 + || contained_in (block_found, + innermost_block)) + innermost_block = block_found; + } write_exp_elt_opcode (OP_VAR_VALUE); /* block_found is set by lookup_symbol. */ -- 2.34.1