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ax_compiler_flags.m4
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ax_compiler_flags.m4
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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_compiler_flags.html
# ===========================================================================
#
# SYNOPSIS
#
# 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])
#
# DESCRIPTION
#
# Check for the presence of an --enable-compile-warnings option to
# configure, defaulting to "error" in normal operation, or "yes" if
# IS-RELEASE is equal to "yes". Return the value in the variable
# $ax_enable_compile_warnings.
#
# Depending on the value of --enable-compile-warnings, different compiler
# warnings are checked to see if they work with the current compiler and,
# if so, are appended to CFLAGS-VARIABLE and LDFLAGS-VARIABLE. This
# allows a consistent set of baseline compiler warnings to be used across
# a code base, irrespective of any warnings enabled locally by individual
# developers. By standardising the warnings used by all developers of a
# project, the project can commit to a zero-warnings policy, using -Werror
# to prevent compilation if new warnings are introduced. This makes
# catching bugs which are flagged by warnings a lot easier.
#
# By providing a consistent --enable-compile-warnings argument across all
# projects using this macro, continuous integration systems can easily be
# configured the same for all projects. Automated systems or build
# systems aimed at beginners may want to pass the --disable-Werror
# argument to unconditionally prevent warnings being fatal.
#
# --enable-compile-warnings can take the values:
#
# * no: Base compiler warnings only; not even -Wall.
# * yes: The above, plus a broad range of useful warnings.
# * error: The above, plus -Werror so that all warnings are fatal.
# Use --disable-Werror to override this and disable fatal
# warnings.
#
# The set of base and enabled flags can be augmented using the
# EXTRA-*-CFLAGS and EXTRA-*-LDFLAGS variables, which are tested and
# appended to the output variable if --enable-compile-warnings is not
# "no". Flags should not be disabled using these arguments, as the entire
# point of AX_COMPILER_FLAGS is to enforce a consistent set of useful
# compiler warnings on code, using warnings which have been chosen for low
# false positive rates. If a compiler emits false positives for a
# warning, a #pragma should be used in the code to disable the warning
# locally. See:
#
# https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas
#
# The EXTRA-* variables should only be used to supply extra warning flags,
# and not general purpose compiler flags, as they are controlled by
# configure options such as --disable-Werror.
#
# IS-RELEASE can be used to disable -Werror when making a release, which
# is useful for those hairy moments when you just want to get the release
# done as quickly as possible. Set it to "yes" to disable -Werror. By
# default, it uses the value of $ax_is_release, so if you are using the
# AX_IS_RELEASE macro, there is no need to pass this parameter. For
# example:
#
# AX_IS_RELEASE([git-directory])
# AX_COMPILER_FLAGS()
#
# CFLAGS-VARIABLE defaults to WARN_CFLAGS, and LDFLAGS-VARIABLE defaults
# to WARN_LDFLAGS. Both variables are AC_SUBST-ed by this macro, but must
# be manually added to the CFLAGS and LDFLAGS variables for each target in
# the code base.
#
# If C++ language support is enabled with AC_PROG_CXX, which must occur
# before this macro in configure.ac, warning flags for the C++ compiler
# are AC_SUBST-ed as WARN_CXXFLAGS, and must be manually added to the
# CXXFLAGS variables for each target in the code base. EXTRA-*-CFLAGS can
# be used to augment the base and enabled flags.
#
# Warning flags for g-ir-scanner (from GObject Introspection) are
# AC_SUBST-ed as WARN_SCANNERFLAGS. This variable must be manually added
# to the SCANNERFLAGS variable for each GIR target in the code base. If
# extra g-ir-scanner flags need to be enabled, the AX_COMPILER_FLAGS_GIR
# macro must be invoked manually.
#
# AX_COMPILER_FLAGS may add support for other tools in future, in addition
# to the compiler and linker. No extra EXTRA-* variables will be added
# for those tools, and all extra support will still use the single
# --enable-compile-warnings configure option. For finer grained control
# over the flags for individual tools, use AX_COMPILER_FLAGS_CFLAGS,
# AX_COMPILER_FLAGS_LDFLAGS and AX_COMPILER_FLAGS_* for new tools.
#
# The UNUSED variables date from a previous version of this macro, and are
# automatically appended to the preceding non-UNUSED variable. They should
# be left empty in new uses of the macro.
#
# LICENSE
#
# Copyright (c) 2014, 2015 Philip Withnall <[email protected]>
# Copyright (c) 2015 David King <[email protected]>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 14
# _AX_COMPILER_FLAGS_LANG([LANGNAME])
m4_defun([_AX_COMPILER_FLAGS_LANG],
[m4_ifdef([_AX_COMPILER_FLAGS_LANG_]$1[_enabled], [],
[m4_define([_AX_COMPILER_FLAGS_LANG_]$1[_enabled], [])dnl
AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS_]$1[FLAGS])])dnl
])
AC_DEFUN([AX_COMPILER_FLAGS],[
# C support is enabled by default.
_AX_COMPILER_FLAGS_LANG([C])
# Only enable C++ support if AC_PROG_CXX is called. The redefinition of
# AC_PROG_CXX is so that a fatal error is emitted if this macro is called
# before AC_PROG_CXX, which would otherwise cause no C++ warnings to be
# checked.
AC_PROVIDE_IFELSE([AC_PROG_CXX],
[_AX_COMPILER_FLAGS_LANG([CXX])],
[m4_define([AC_PROG_CXX], defn([AC_PROG_CXX])[_AX_COMPILER_FLAGS_LANG([CXX])])])
AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS_LDFLAGS])
# Default value for IS-RELEASE is $ax_is_release
ax_compiler_flags_is_release=m4_tolower(m4_normalize(ifelse([$3],,
[$ax_is_release],
[$3])))
AC_ARG_ENABLE([compile-warnings],
AS_HELP_STRING([--enable-compile-warnings=@<:@no/yes/error@:>@],
[Enable compiler warnings and errors]),,
[AS_IF([test "$ax_compiler_flags_is_release" = "yes"],
[enable_compile_warnings="yes"],
[enable_compile_warnings="error"])])
AC_ARG_ENABLE([Werror],
AS_HELP_STRING([--disable-Werror],
[Unconditionally make all compiler warnings non-fatal]),,
[enable_Werror=maybe])
# Return the user's chosen warning level
AS_IF([test "$enable_Werror" = "no" -a \
"$enable_compile_warnings" = "error"],[
enable_compile_warnings="yes"
])
ax_enable_compile_warnings=$enable_compile_warnings
AX_COMPILER_FLAGS_CFLAGS([$1],[$ax_compiler_flags_is_release],
[$4],[$5 $6 $7 $8])
m4_ifdef([_AX_COMPILER_FLAGS_LANG_CXX_enabled],
[AX_COMPILER_FLAGS_CXXFLAGS([WARN_CXXFLAGS],
[$ax_compiler_flags_is_release],
[$4],[$5 $6 $7 $8])])
AX_COMPILER_FLAGS_LDFLAGS([$2],[$ax_compiler_flags_is_release],
[$9],[$10 $11 $12 $13])
AX_COMPILER_FLAGS_GIR([WARN_SCANNERFLAGS],[$ax_compiler_flags_is_release])
])dnl AX_COMPILER_FLAGS