Blame m4/warn-on-use.m4

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# warn-on-use.m4 serial 5
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dnl Copyright (C) 2010-2015 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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# gl_WARN_ON_USE_PREPARE(INCLUDES, NAMES)
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# ---------------------------------------
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# For each whitespace-separated element in the list of NAMES, define
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# HAVE_RAW_DECL_name if the function has a declaration among INCLUDES
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# even after being undefined as a macro.
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#
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# See warn-on-use.h for some hints on how to poison function names, as
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# well as ideas on poisoning global variables and macros.  NAMES may
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# include global variables, but remember that only functions work with
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# _GL_WARN_ON_USE.  Typically, INCLUDES only needs to list a single
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# header, but if the replacement header pulls in other headers because
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# some systems declare functions in the wrong header, then INCLUDES
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# should do likewise.
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#
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# It is generally safe to assume declarations for functions declared
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# in the intersection of C89 and C11 (such as printf) without
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# needing gl_WARN_ON_USE_PREPARE.
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AC_DEFUN([gl_WARN_ON_USE_PREPARE],
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[
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  m4_foreach_w([gl_decl], [$2],
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    [AH_TEMPLATE([HAVE_RAW_DECL_]AS_TR_CPP(m4_defn([gl_decl])),
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      [Define to 1 if ]m4_defn([gl_decl])[ is declared even after
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       undefining macros.])])dnl
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dnl FIXME: gl_Symbol must be used unquoted until we can assume
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dnl autoconf 2.64 or newer.
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  for gl_func in m4_flatten([$2]); do
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    AS_VAR_PUSHDEF([gl_Symbol], [gl_cv_have_raw_decl_$gl_func])dnl
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    AC_CACHE_CHECK([whether $gl_func is declared without a macro],
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      gl_Symbol,
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      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([$1],
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[@%:@undef $gl_func
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  (void) $gl_func;])],
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        [AS_VAR_SET(gl_Symbol, [yes])], [AS_VAR_SET(gl_Symbol, [no])])])
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    AS_VAR_IF(gl_Symbol, [yes],
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      [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_RAW_DECL_$gl_func]), [1])
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       dnl shortcut - if the raw declaration exists, then set a cache
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       dnl variable to allow skipping any later AC_CHECK_DECL efforts
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       eval ac_cv_have_decl_$gl_func=yes])
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    AS_VAR_POPDEF([gl_Symbol])dnl
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  done
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])