m4/ax_compiler_flags.m4

   1 # ===========================================================================
   2 #    https://www.gnu.org/software/autoconf-archive/ax_compiler_flags.html
   3 # ===========================================================================
   4 #
   5 # SYNOPSIS
   6 #
   7 #   AX_COMPILER_FLAGS([CFLAGS-VARIABLE], [LDFLAGS-VARIABLE], [IS-RELEASE], [EXTRA-BASE-CFLAGS], [EXTRA-YES-CFLAGS], [UNUSED], [UNUSED], [UNUSED], [EXTRA-BASE-LDFLAGS], [EXTRA-YES-LDFLAGS], [UNUSED], [UNUSED], [UNUSED])
   8 #
   9 # DESCRIPTION
  10 #
  11 #   Check for the presence of an --enable-compile-warnings option to
  12 #   configure, defaulting to "error" in normal operation, or "yes" if
  13 #   IS-RELEASE is equal to "yes".  Return the value in the variable
  14 #   $ax_enable_compile_warnings.
  15 #
  16 #   Depending on the value of --enable-compile-warnings, different compiler
  17 #   warnings are checked to see if they work with the current compiler and,
  18 #   if so, are appended to CFLAGS-VARIABLE and LDFLAGS-VARIABLE.  This
  19 #   allows a consistent set of baseline compiler warnings to be used across
  20 #   a code base, irrespective of any warnings enabled locally by individual
  21 #   developers.  By standardising the warnings used by all developers of a
  22 #   project, the project can commit to a zero-warnings policy, using -Werror
  23 #   to prevent compilation if new warnings are introduced.  This makes
  24 #   catching bugs which are flagged by warnings a lot easier.
  25 #
  26 #   By providing a consistent --enable-compile-warnings argument across all
  27 #   projects using this macro, continuous integration systems can easily be
  28 #   configured the same for all projects.  Automated systems or build
  29 #   systems aimed at beginners may want to pass the --disable-Werror
  30 #   argument to unconditionally prevent warnings being fatal.
  31 #
  32 #   --enable-compile-warnings can take the values:
  33 #
  34 #    * no:      Base compiler warnings only; not even -Wall.
  35 #    * yes:     The above, plus a broad range of useful warnings.
  36 #    * error:   The above, plus -Werror so that all warnings are fatal.
  37 #               Use --disable-Werror to override this and disable fatal
  38 #               warnings.
  39 #
  40 #   The set of base and enabled flags can be augmented using the
  41 #   EXTRA-*-CFLAGS and EXTRA-*-LDFLAGS variables, which are tested and
  42 #   appended to the output variable if --enable-compile-warnings is not
  43 #   "no". Flags should not be disabled using these arguments, as the entire
  44 #   point of AX_COMPILER_FLAGS is to enforce a consistent set of useful
  45 #   compiler warnings on code, using warnings which have been chosen for low
  46 #   false positive rates.  If a compiler emits false positives for a
  47 #   warning, a #pragma should be used in the code to disable the warning
  48 #   locally. See:
  49 #
  50 #     https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas
  51 #
  52 #   The EXTRA-* variables should only be used to supply extra warning flags,
  53 #   and not general purpose compiler flags, as they are controlled by
  54 #   configure options such as --disable-Werror.
  55 #
  56 #   IS-RELEASE can be used to disable -Werror when making a release, which
  57 #   is useful for those hairy moments when you just want to get the release
  58 #   done as quickly as possible.  Set it to "yes" to disable -Werror. By
  59 #   default, it uses the value of $ax_is_release, so if you are using the
  60 #   AX_IS_RELEASE macro, there is no need to pass this parameter. For
  61 #   example:
  62 #
  63 #     AX_IS_RELEASE([git-directory])
  64 #     AX_COMPILER_FLAGS()
  65 #
  66 #   CFLAGS-VARIABLE defaults to WARN_CFLAGS, and LDFLAGS-VARIABLE defaults
  67 #   to WARN_LDFLAGS.  Both variables are AC_SUBST-ed by this macro, but must
  68 #   be manually added to the CFLAGS and LDFLAGS variables for each target in
  69 #   the code base.
  70 #
  71 #   If C++ language support is enabled with AC_PROG_CXX, which must occur
  72 #   before this macro in configure.ac, warning flags for the C++ compiler
  73 #   are AC_SUBST-ed as WARN_CXXFLAGS, and must be manually added to the
  74 #   CXXFLAGS variables for each target in the code base.  EXTRA-*-CFLAGS can
  75 #   be used to augment the base and enabled flags.
  76 #
  77 #   Warning flags for g-ir-scanner (from GObject Introspection) are
  78 #   AC_SUBST-ed as WARN_SCANNERFLAGS.  This variable must be manually added
  79 #   to the SCANNERFLAGS variable for each GIR target in the code base.  If
  80 #   extra g-ir-scanner flags need to be enabled, the AX_COMPILER_FLAGS_GIR
  81 #   macro must be invoked manually.
  82 #
  83 #   AX_COMPILER_FLAGS may add support for other tools in future, in addition
  84 #   to the compiler and linker.  No extra EXTRA-* variables will be added
  85 #   for those tools, and all extra support will still use the single
  86 #   --enable-compile-warnings configure option.  For finer grained control
  87 #   over the flags for individual tools, use AX_COMPILER_FLAGS_CFLAGS,
  88 #   AX_COMPILER_FLAGS_LDFLAGS and AX_COMPILER_FLAGS_* for new tools.
  89 #
  90 #   The UNUSED variables date from a previous version of this macro, and are
  91 #   automatically appended to the preceding non-UNUSED variable. They should
  92 #   be left empty in new uses of the macro.
  93 #
  94 # LICENSE
  95 #
  96 #   Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
  97 #   Copyright (c) 2015 David King <amigadave@amigadave.com>
  98 #
  99 #   Copying and distribution of this file, with or without modification, are
 100 #   permitted in any medium without royalty provided the copyright notice
 101 #   and this notice are preserved.  This file is offered as-is, without any
 102 #   warranty.
 103
 104 #serial 14
 105
 106 # _AX_COMPILER_FLAGS_LANG([LANGNAME])
 107 m4_defun([_AX_COMPILER_FLAGS_LANG],
 108 [m4_ifdef([_AX_COMPILER_FLAGS_LANG_]$1[_enabled], [],
 109           [m4_define([_AX_COMPILER_FLAGS_LANG_]$1[_enabled], [])dnl
 110            AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS_]$1[FLAGS])])dnl
 111 ])
 112
 113 AC_DEFUN([AX_COMPILER_FLAGS],[
 114     # C support is enabled by default.
 115     _AX_COMPILER_FLAGS_LANG([C])
 116     # Only enable C++ support if AC_PROG_CXX is called. The redefinition of
 117     # AC_PROG_CXX is so that a fatal error is emitted if this macro is called
 118     # before AC_PROG_CXX, which would otherwise cause no C++ warnings to be
 119     # checked.
 120     AC_PROVIDE_IFELSE([AC_PROG_CXX],
 121                       [_AX_COMPILER_FLAGS_LANG([CXX])],
 122                       [m4_define([AC_PROG_CXX], defn([AC_PROG_CXX])[_AX_COMPILER_FLAGS_LANG([CXX])])])
 123     AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS_LDFLAGS])
 124
 125     # Default value for IS-RELEASE is $ax_is_release
 126     ax_compiler_flags_is_release=m4_tolower(m4_normalize(ifelse([$3],,
 127                                                                 [$ax_is_release],
 128                                                                 [$3])))
 129
 130     AC_ARG_ENABLE([compile-warnings],
 131                   AS_HELP_STRING([--enable-compile-warnings=@<:@no/yes/error@:>@],
 132                                  [Enable compiler warnings and errors]),,
 133                   [AS_IF([test "$ax_compiler_flags_is_release" = "yes"],
 134                          [enable_compile_warnings="yes"],
 135                          [enable_compile_warnings="error"])])
 136     AC_ARG_ENABLE([Werror],
 137                   AS_HELP_STRING([--disable-Werror],
 138                                  [Unconditionally make all compiler warnings non-fatal]),,
 139                   [enable_Werror=maybe])
 140
 141     # Return the user's chosen warning level
 142     AS_IF([test "$enable_Werror" = "no" -a \
 143                 "$enable_compile_warnings" = "error"],[
 144         enable_compile_warnings="yes"
 145     ])
 146
 147     ax_enable_compile_warnings=$enable_compile_warnings
 148
 149     AX_COMPILER_FLAGS_CFLAGS([$1],[$ax_compiler_flags_is_release],
 150                              [$4],[$5 $6 $7 $8])
 151     m4_ifdef([_AX_COMPILER_FLAGS_LANG_CXX_enabled],
 152              [AX_COMPILER_FLAGS_CXXFLAGS([WARN_CXXFLAGS],
 153                                          [$ax_compiler_flags_is_release],
 154                                          [$4],[$5 $6 $7 $8])])
 155     AX_COMPILER_FLAGS_LDFLAGS([$2],[$ax_compiler_flags_is_release],
 156                               [$9],[$10 $11 $12 $13])
 157     AX_COMPILER_FLAGS_GIR([WARN_SCANNERFLAGS],[$ax_compiler_flags_is_release])
 158 ])dnl AX_COMPILER_FLAGS