1 # ==============================================================================
2 # https://www.gnu.org/software/autoconf-archive/ax_compiler_flags_ldflags.html
3 # ==============================================================================
7 # AX_COMPILER_FLAGS_LDFLAGS([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-YES-FLAGS])
11 # Add warning flags for the linker to VARIABLE, which defaults to
12 # WARN_LDFLAGS. VARIABLE is AC_SUBST-ed by this macro, but must be
13 # manually added to the LDFLAGS 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_LDFLAGS],[
31 AX_REQUIRE_DEFINED([AX_APPEND_LINK_FLAGS])
32 AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
33 AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
34 AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
37 m4_define([ax_warn_ldflags_variable],
38 [m4_normalize(ifelse([$1],,[WARN_LDFLAGS],[$1]))])
40 # Always pass -Werror=unknown-warning-option to get Clang to fail on bad
41 # flags, otherwise they are always appended to the warn_ldflags variable,
42 # and Clang warns on them for every compilation unit.
43 # If this is passed to GCC, it will explode, so the flag must be enabled
45 AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option],[
46 ax_compiler_flags_test="-Werror=unknown-warning-option"
48 ax_compiler_flags_test=""
51 # macOS linker does not have --as-needed
52 AX_CHECK_LINK_FLAG([-Wl,--no-as-needed], [
53 ax_compiler_flags_as_needed_option="-Wl,--no-as-needed"
55 ax_compiler_flags_as_needed_option=""
58 # macOS linker speaks with a different accent
59 ax_compiler_flags_fatal_warnings_option=""
60 AX_CHECK_LINK_FLAG([-Wl,--fatal-warnings], [
61 ax_compiler_flags_fatal_warnings_option="-Wl,--fatal-warnings"
63 AX_CHECK_LINK_FLAG([-Wl,-fatal_warnings], [
64 ax_compiler_flags_fatal_warnings_option="-Wl,-fatal_warnings"
68 AX_APPEND_LINK_FLAGS([ dnl
69 $ax_compiler_flags_as_needed_option dnl
71 ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
73 AS_IF([test "$ax_enable_compile_warnings" != "no"],[
75 AX_APPEND_LINK_FLAGS([$4 $5 $6 $7],
76 ax_warn_ldflags_variable,
77 [$ax_compiler_flags_test])
79 AS_IF([test "$ax_enable_compile_warnings" = "error"],[
80 # "error" flags; -Werror has to be appended unconditionally because
81 # it's not possible to test for
83 # suggest-attribute=format is disabled because it gives too many false
85 AX_APPEND_LINK_FLAGS([ dnl
86 $ax_compiler_flags_fatal_warnings_option dnl
87 ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
90 # Substitute the variables
91 AC_SUBST(ax_warn_ldflags_variable)
92 ])dnl AX_COMPILER_FLAGS