1 # ============================================================================
2 # http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cflags.html
3 # ============================================================================
7 # AX_COMPILER_FLAGS_CFLAGS([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-MINIMUM-FLAGS], [EXTRA-YES-FLAGS], [EXTRA-MAXIMUM-FLAGS], [EXTRA-ERROR-FLAGS])
11 # Add warning flags for the C compiler to VARIABLE, which defaults to
12 # WARN_CFLAGS. VARIABLE is AC_SUBST-ed by this macro, but must be
13 # manually added to the CFLAGS variable for each target in the code base.
15 # This macro depends on the environment set up by AX_COMPILER_FLAGS.
16 # Specifically, it uses the value of $ax_enable_compile_warnings to decide
17 # which flags to enable.
21 # Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
23 # Copying and distribution of this file, with or without modification, are
24 # permitted in any medium without royalty provided the copyright notice
25 # and this notice are preserved. This file is offered as-is, without any
30 AC_DEFUN([AX_COMPILER_FLAGS_CFLAGS],[
31 AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
32 AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
33 AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
36 m4_define(ax_warn_cflags_variable,
37 [m4_normalize(ifelse([$1],,[WARN_CFLAGS],[$1]))])
41 # Always pass -Werror=unknown-warning-option to get Clang to fail on bad
42 # flags, otherwise they are always appended to the warn_cflags variable, and
43 # Clang warns on them for every compilation unit.
44 # If this is passed to GCC, it will explode, so the flag must be enabled
46 AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option],[
47 ax_compiler_flags_test="-Werror=unknown-warning-option"
49 ax_compiler_flags_test=""
53 AX_APPEND_COMPILE_FLAGS([ dnl
54 -fno-strict-aliasing dnl
56 ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
58 # In the flags below, when disabling specific flags, always add *both*
59 # -Wno-foo and -Wno-error=foo. This fixes the situation where (for example)
60 # we enable -Werror, disable a flag, and a build bot passes CFLAGS=-Wall,
61 # which effectively turns that flag back on again as an error.
62 AS_IF([test "$ax_enable_compile_warnings" != "no"],[
64 AX_APPEND_COMPILE_FLAGS([ dnl
67 ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
69 AS_IF([test "$ax_enable_compile_warnings" != "no" -a \
70 "$ax_enable_compile_warnings" != "minimum"],[
72 AX_APPEND_COMPILE_FLAGS([ dnl
78 -Wmissing-declarations dnl
79 -Wmissing-prototypes dnl
80 -Wstrict-prototypes dnl
82 -Wno-unused-parameter dnl
83 -Wno-error=unused-parameter dnl
84 -Wno-missing-field-initializers dnl
85 -Wno-error=missing-field-initializers dnl
86 -Wdeclaration-after-statement dnl
88 -Wold-style-definition dnl
90 -Wformat-nonliteral dnl
97 -Wmissing-format-attribute dnl
98 -Wmissing-noreturn dnl
100 -Wredundant-decls dnl
101 -Wmissing-include-dirs dnl
102 -Wunused-but-set-variable dnl
104 -Wimplicit-function-declaration dnl
107 ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
109 AS_IF([test "$ax_enable_compile_warnings" = "maximum" -o \
110 "$ax_enable_compile_warnings" = "error"],[
112 AX_APPEND_COMPILE_FLAGS([ dnl
115 -Waggregate-return dnl
117 ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
119 AS_IF([test "$ax_enable_compile_warnings" = "error"],[
120 # "error" flags; -Werror has to be appended unconditionally because
121 # it’s not possible to test for
123 # suggest-attribute=format is disabled because it gives too many false
125 AX_APPEND_FLAG([-Werror],ax_warn_cflags_variable)
127 AX_APPEND_COMPILE_FLAGS([ dnl
128 -Wno-suggest-attribute=format dnl
130 ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
135 # Substitute the variables
136 AC_SUBST(ax_warn_cflags_variable)
137 ])dnl AX_COMPILER_FLAGS