Blame m4/ax_compiler_flags_ldflags.m4

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# =============================================================================
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#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_ldflags.html
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# =============================================================================
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#
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# SYNOPSIS
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#
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#   AX_COMPILER_FLAGS_LDFLAGS([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-YES-FLAGS])
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#
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# DESCRIPTION
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#
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#   Add warning flags for the linker to VARIABLE, which defaults to
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#   WARN_LDFLAGS.  VARIABLE is AC_SUBST-ed by this macro, but must be
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#   manually added to the LDFLAGS variable for each target in the code base.
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#
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#   This macro depends on the environment set up by AX_COMPILER_FLAGS.
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#   Specifically, it uses the value of $ax_enable_compile_warnings to decide
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#   which flags to enable.
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#
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# LICENSE
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#
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#   Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
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#
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#   Copying and distribution of this file, with or without modification, are
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#   permitted in any medium without royalty provided the copyright notice
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#   and this notice are preserved.  This file is offered as-is, without any
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#   warranty.
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#serial 4
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AC_DEFUN([AX_COMPILER_FLAGS_LDFLAGS],[
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    AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
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    AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
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    AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
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    # Variable names
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    m4_define(ax_warn_ldflags_variable,
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              [m4_normalize(ifelse([$1],,[WARN_LDFLAGS],[$1]))])
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    # Always pass -Werror=unknown-warning-option to get Clang to fail on bad
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    # flags, otherwise they are always appended to the warn_ldflags variable,
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    # and Clang warns on them for every compilation unit.
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    # If this is passed to GCC, it will explode, so the flag must be enabled
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    # conditionally.
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    AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option],[
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        ax_compiler_flags_test="-Werror=unknown-warning-option"
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    ],[
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        ax_compiler_flags_test=""
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    ])
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    # Base flags
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    AX_APPEND_COMPILE_FLAGS([ dnl
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        -Wl,--no-as-needed dnl
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        $3 dnl
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    ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
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    AS_IF([test "$ax_enable_compile_warnings" != "no"],[
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        # "yes" flags
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        AX_APPEND_COMPILE_FLAGS([$4 $5 $6 $7],
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                                ax_warn_ldflags_variable,
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                                [$ax_compiler_flags_test])
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    ])
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    AS_IF([test "$ax_enable_compile_warnings" = "error"],[
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        # "error" flags; -Werror has to be appended unconditionally because
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        # it's not possible to test for
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        #
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        # suggest-attribute=format is disabled because it gives too many false
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        # positives
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        AX_APPEND_COMPILE_FLAGS([ dnl
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            -Wl,--fatal-warnings dnl
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        ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
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    ])
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    # Substitute the variables
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    AC_SUBST(ax_warn_ldflags_variable)
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])dnl AX_COMPILER_FLAGS