[Buildroot] [PATCH] package/flex: fix build with old host GCC since autoconf bump

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Since the bump of autoconf to version 2.73 in Buildroot commit, the
build of target flex fails if the host compiler is too old, because
the flex build system tries to use -std=gnu23 which isn't supported by
older GCC releases, causing:

gcc: error: unrecognized command-line option '-std=gnu23'; did you mean '-std=gnu2x'?
gcc: error: unrecognized command-line option '-std=gnu23'; did you mean '-std=gnu2x'?
make[3]: *** [Makefile:1162: stage1flex-buf.o] Error 1

(Indeed the *target* flex package does build some host tools using the
host GCC compiler.)

To fix this issue, we backport an upstream commit that isn't yet in
any flex release.

Fixes:

  https://autobuild.buildroot.net/results/aac730b57adb5b54964f1054de781750952ef7d4/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
---
 ...PROG_CC_FOR_BUILD-to-fix-BUILD_EXEEX.patch | 184 ++++++++++++++++++
 1 file changed, 184 insertions(+)
 create mode 100644 package/flex/0005-build-Update-AX_PROG_CC_FOR_BUILD-to-fix-BUILD_EXEEX.patch

diff --git a/package/flex/0005-build-Update-AX_PROG_CC_FOR_BUILD-to-fix-BUILD_EXEEX.patch b/package/flex/0005-build-Update-AX_PROG_CC_FOR_BUILD-to-fix-BUILD_EXEEX.patch
new file mode 100644
index 0000000000..c3a90637b9
--- /dev/null
+++ b/package/flex/0005-build-Update-AX_PROG_CC_FOR_BUILD-to-fix-BUILD_EXEEX.patch
@@ -0,0 +1,184 @@
+From 5f441f438f086553698e899fa0a475dbb0237d02 Mon Sep 17 00:00:00 2001
+From: Explorer09 <explorer09@gmail.com>
+Date: Wed, 8 May 2024 21:04:01 +0800
+Subject: [PATCH] build: Update AX_PROG_CC_FOR_BUILD to fix BUILD_EXEEXT
+ problems
+
+Upstream: 787edd41833e14e986ff093f7216e7005aca5fe2
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+---
+ m4/ax_prog_cc_for_build.m4 | 102 ++++++++++++++++++++++++++++---------
+ 1 file changed, 77 insertions(+), 25 deletions(-)
+
+diff --git a/m4/ax_prog_cc_for_build.m4 b/m4/ax_prog_cc_for_build.m4
+index 77fd346..3d28252 100644
+--- a/m4/ax_prog_cc_for_build.m4
++++ b/m4/ax_prog_cc_for_build.m4
+@@ -1,5 +1,5 @@
+ # ===========================================================================
+-#   http://www.gnu.org/software/autoconf-archive/ax_prog_cc_for_build.html
++#   https://www.gnu.org/software/autoconf-archive/ax_prog_cc_for_build.html
+ # ===========================================================================
+ #
+ # SYNOPSIS
+@@ -32,28 +32,34 @@
+ #   and this notice are preserved. This file is offered as-is, without any
+ #   warranty.
+ 
+-#serial 8
++#serial 21
++# With patches not yet merged upstream
++# <https://savannah.gnu.org/patch/index.php?10452>
+ 
+ AU_ALIAS([AC_PROG_CC_FOR_BUILD], [AX_PROG_CC_FOR_BUILD])
+ AC_DEFUN([AX_PROG_CC_FOR_BUILD], [dnl
+ AC_REQUIRE([AC_PROG_CC])dnl
+ AC_REQUIRE([AC_PROG_CPP])dnl
+-AC_REQUIRE([AC_EXEEXT])dnl
+-AC_REQUIRE([AC_CANONICAL_HOST])dnl
++AC_REQUIRE([AC_CANONICAL_BUILD])dnl
+ 
+ dnl Use the standard macros, but make them use other variable names
+ dnl
+ pushdef([ac_cv_prog_CPP], ac_cv_build_prog_CPP)dnl
+ pushdef([ac_cv_prog_gcc], ac_cv_build_prog_gcc)dnl
++pushdef([ac_cv_prog_cc_c89], ac_cv_build_prog_cc_c89)dnl
++pushdef([ac_cv_prog_cc_c99], ac_cv_build_prog_cc_c99)dnl
++pushdef([ac_cv_prog_cc_c11], ac_cv_build_prog_cc_c11)dnl
++pushdef([ac_cv_prog_cc_c23], ac_cv_build_prog_cc_c23)dnl
++pushdef([ac_cv_prog_cc_stdc], ac_cv_build_prog_cc_stdc)dnl
+ pushdef([ac_cv_prog_cc_works], ac_cv_build_prog_cc_works)dnl
+ pushdef([ac_cv_prog_cc_cross], ac_cv_build_prog_cc_cross)dnl
+ pushdef([ac_cv_prog_cc_g], ac_cv_build_prog_cc_g)dnl
+-pushdef([ac_cv_exeext], ac_cv_build_exeext)dnl
+-pushdef([ac_cv_objext], ac_cv_build_objext)dnl
++pushdef([ac_prog_cc_stdc], ac_build_prog_cc_stdc)dnl
+ pushdef([ac_exeext], ac_build_exeext)dnl
+ pushdef([ac_objext], ac_build_objext)dnl
+ pushdef([CC], CC_FOR_BUILD)dnl
+ pushdef([CPP], CPP_FOR_BUILD)dnl
++pushdef([GCC], GCC_FOR_BUILD)dnl
+ pushdef([CFLAGS], CFLAGS_FOR_BUILD)dnl
+ pushdef([CPPFLAGS], CPPFLAGS_FOR_BUILD)dnl
+ pushdef([LDFLAGS], LDFLAGS_FOR_BUILD)dnl
+@@ -67,27 +73,58 @@ pushdef([ac_cv_host_alias], ac_cv_build_alias)dnl
+ pushdef([ac_cv_host_cpu], ac_cv_build_cpu)dnl
+ pushdef([ac_cv_host_vendor], ac_cv_build_vendor)dnl
+ pushdef([ac_cv_host_os], ac_cv_build_os)dnl
+-pushdef([ac_cpp], ac_build_cpp)dnl
+-pushdef([ac_compile], ac_build_compile)dnl
+-pushdef([ac_link], ac_build_link)dnl
++pushdef([ac_tool_prefix], ac_build_tool_prefix)dnl
++pushdef([am_cv_CC_dependencies_compiler_type], am_cv_build_CC_dependencies_compiler_type)dnl
++pushdef([am_cv_prog_cc_c_o], am_cv_build_prog_cc_c_o)dnl
++pushdef([cross_compiling], cross_compiling_build)dnl
++dnl
++dnl These variables are problematic to rename by M4 macros, so we save
++dnl their values in alternative names, and restore the values later.
++dnl
++dnl _AC_COMPILER_EXEEXT and _AC_COMPILER_OBJEXT internally call
++dnl AC_SUBST which prevents the renaming of EXEEXT and OBJEXT
++dnl variables. It's not a good idea to rename ac_cv_exeext and
++dnl ac_cv_objext either as they're related.
++dnl Renaming ac_exeext and ac_objext is safe though.
++dnl
++ac_cv_host_exeext=$ac_cv_exeext
++AS_VAR_SET_IF([ac_cv_build_exeext],
++  [ac_cv_exeext=$ac_cv_build_exeext],
++  [AS_UNSET([ac_cv_exeext])])
++ac_cv_host_objext=$ac_cv_objext
++AS_VAR_SET_IF([ac_cv_build_objext],
++  [ac_cv_objext=$ac_cv_build_objext],
++  [AS_UNSET([ac_cv_objext])])
++dnl
++dnl ac_cv_c_compiler_gnu is used in _AC_LANG_COMPILER_GNU (called by
++dnl AC_PROG_CC) indirectly.
++dnl
++ac_cv_host_c_compiler_gnu=$ac_cv_c_compiler_gnu
++AS_VAR_SET_IF([ac_cv_build_c_compiler_gnu],
++  [ac_cv_c_compiler_gnu=$ac_cv_build_c_compiler_gnu],
++  [AS_UNSET([ac_cv_c_compiler_gnu])])
++
++cross_compiling_build=no
+ 
+-save_cross_compiling=$cross_compiling
+-save_ac_tool_prefix=$ac_tool_prefix
+-cross_compiling=no
+-ac_tool_prefix=
++ac_build_tool_prefix=
++AS_IF([test -n "$build"],      [ac_build_tool_prefix="$build-"],
++      [test -n "$build_alias"],[ac_build_tool_prefix="$build_alias-"])
+ 
++AC_LANG_PUSH([C])
+ AC_PROG_CC
++_AC_COMPILER_EXEEXT
++_AC_COMPILER_OBJEXT
+ AC_PROG_CPP
+-AC_EXEEXT
+ 
+-ac_tool_prefix=$save_ac_tool_prefix
+-cross_compiling=$save_cross_compiling
++BUILD_EXEEXT=$ac_cv_exeext
++BUILD_OBJEXT=$ac_cv_objext
+ 
+ dnl Restore the old definitions
+ dnl
+-popdef([ac_link])dnl
+-popdef([ac_compile])dnl
+-popdef([ac_cpp])dnl
++popdef([cross_compiling])dnl
++popdef([am_cv_prog_cc_c_o])dnl
++popdef([am_cv_CC_dependencies_compiler_type])dnl
++popdef([ac_tool_prefix])dnl
+ popdef([ac_cv_host_os])dnl
+ popdef([ac_cv_host_vendor])dnl
+ popdef([ac_cv_host_cpu])dnl
+@@ -101,24 +138,39 @@ popdef([host])dnl
+ popdef([LDFLAGS])dnl
+ popdef([CPPFLAGS])dnl
+ popdef([CFLAGS])dnl
++popdef([GCC])dnl
+ popdef([CPP])dnl
+ popdef([CC])dnl
+ popdef([ac_objext])dnl
+ popdef([ac_exeext])dnl
+-popdef([ac_cv_objext])dnl
+-popdef([ac_cv_exeext])dnl
++popdef([ac_prog_cc_stdc])dnl
+ popdef([ac_cv_prog_cc_g])dnl
+ popdef([ac_cv_prog_cc_cross])dnl
+ popdef([ac_cv_prog_cc_works])dnl
++popdef([ac_cv_prog_cc_stdc])dnl
++popdef([ac_cv_prog_cc_c23])dnl
++popdef([ac_cv_prog_cc_c11])dnl
++popdef([ac_cv_prog_cc_c99])dnl
++popdef([ac_cv_prog_cc_c89])dnl
+ popdef([ac_cv_prog_gcc])dnl
+ popdef([ac_cv_prog_CPP])dnl
++dnl
++ac_cv_exeext=$ac_cv_host_exeext
++EXEEXT=$ac_cv_host_exeext
++ac_cv_objext=$ac_cv_host_objext
++OBJEXT=$ac_cv_host_objext
++ac_cv_c_compiler_gnu=$ac_cv_host_c_compiler_gnu
++ac_compiler_gnu=$ac_cv_host_c_compiler_gnu
++
++dnl restore global variables ac_ext, ac_cpp, ac_compile,
++dnl ac_link, ac_compiler_gnu (dependant on the current
++dnl language after popping):
++AC_LANG_POP([C])
+ 
+ dnl Finally, set Makefile variables
+ dnl
+-BUILD_EXEEXT=$ac_build_exeext
+-BUILD_OBJEXT=$ac_build_objext
+-AC_SUBST(BUILD_EXEEXT)dnl
+-AC_SUBST(BUILD_OBJEXT)dnl
++AC_SUBST([BUILD_EXEEXT])dnl
++AC_SUBST([BUILD_OBJEXT])dnl
+ AC_SUBST([CFLAGS_FOR_BUILD])dnl
+ AC_SUBST([CPPFLAGS_FOR_BUILD])dnl
+ AC_SUBST([LDFLAGS_FOR_BUILD])dnl
+-- 
+2.55.0
+
-- 
2.55.0

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