build: Fix AX_PROG_{CC,CXX}_FOR_BUILD macros

Override the cross_compiling and ac_tool_prefix variables by reassigning
to them instead of redefining the macros. Redefining them will actually
cause the variable names to be replaced instead of their content.

Furthermore push the definition of CPPFLAGS before running the checks
for the build tools to avoid the host CPPFLAGS from leaking into the
build CPPFLAGS.

While at it drop the redefinition of AC_TRY_COMPILER which hasn't been
used since autoconf 2.50 and make sure that all definitions are properly
popped when done (LDFLAGS, ac_cv_prog_CPP, ac_cv_prog_CXXCPP).

Acked-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

2 files changed, 23 insertions, 52 deletions

diff --git a/m4/ax_prog_cc_for_build.m4 b/m4/ax_prog_cc_for_build.m4
index 08095a83df..6369809aad 100644
--- a/m4/ax_prog_cc_for_build.m4
+++ b/m4/ax_prog_cc_for_build.m4
@@ -40,30 +40,9 @@ AC_REQUIRE([AC_PROG_CC])dnl
 AC_REQUIRE([AC_PROG_CPP])dnl
 AC_REQUIRE([AC_EXEEXT])dnl
 AC_REQUIRE([AC_CANONICAL_SYSTEM])dnl
-dnl
-pushdef([AC_TRY_COMPILER], [
-cat > conftest.$ac_ext << EOF
-#line __oline__ "configure"
-#include "confdefs.h"
-[$1]
-EOF
-# If we can't run a trivial program, we are probably using a cross
-compiler.
-# Fail miserably.
-if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext} && (./conftest;
-exit) 2>/dev/null; then
-  [$2]=yes
-else
-  echo "configure: failed program was:" >&AC_FD_CC
-  cat conftest.$ac_ext >&AC_FD_CC
-  [$2]=no
-fi
-[$3]=no
-rm -fr conftest*])dnl
 
 dnl Use the standard macros, but make them use other variable names
 dnl
-pushdef([cross_compiling], [#])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_works], ac_cv_build_prog_cc_works)dnl
@@ -91,16 +70,21 @@ 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], [#])dnl
+
+save_cross_compiling=$cross_compiling
+save_ac_tool_prefix=$ac_tool_prefix
+cross_compiling=no
+ac_tool_prefix=
 
 AC_PROG_CC
 AC_PROG_CPP
 AC_EXEEXT
 
+ac_tool_prefix=$save_ac_tool_prefix
+cross_compiling=$save_cross_compiling
+
 dnl Restore the old definitions
 dnl
-popdef([AC_TRY_COMPILER])dnl
-popdef([ac_tool_prefix])dnl
 popdef([ac_link])dnl
 popdef([ac_compile])dnl
 popdef([ac_cpp])dnl
@@ -114,6 +98,7 @@ popdef([host_vendor])dnl
 popdef([host_cpu])dnl
 popdef([host_alias])dnl
 popdef([host])dnl
+popdef([LDFLAGS])dnl
 popdef([CPPFLAGS])dnl
 popdef([CFLAGS])dnl
 popdef([CPP])dnl
@@ -123,10 +108,10 @@ popdef([ac_exeext])dnl
 popdef([ac_cv_objext])dnl
 popdef([ac_cv_exeext])dnl
 popdef([ac_cv_prog_cc_g])dnl
-popdef([ac_cv_prog_cc_works])dnl
 popdef([ac_cv_prog_cc_cross])dnl
+popdef([ac_cv_prog_cc_works])dnl
 popdef([ac_cv_prog_gcc])dnl
-popdef([cross_compiling])dnl
+popdef([ac_cv_prog_CPP])dnl
 
 dnl Finally, set Makefile variables
 dnl
diff --git a/m4/ax_prog_cxx_for_build.m4 b/m4/ax_prog_cxx_for_build.m4
index 4a099f9fbd..ecf8db94e4 100644
--- a/m4/ax_prog_cxx_for_build.m4
+++ b/m4/ax_prog_cxx_for_build.m4
@@ -38,30 +38,9 @@ AC_REQUIRE([AX_PROG_CC_FOR_BUILD])dnl
 AC_REQUIRE([AC_PROG_CXX])dnl
 AC_REQUIRE([AC_PROG_CXXCPP])dnl
 AC_REQUIRE([AC_CANONICAL_SYSTEM])dnl
-dnl
-pushdef([AC_TRY_COMPILER], [
-cat > conftest.$ac_ext << EOF
-#line __oline__ "configure"
-#include "confdefs.h"
-[$1]
-EOF
-# If we can't run a trivial program, we are probably using a cross
-compiler.
-# Fail miserably.
-if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext} && (./conftest;
-exit) 2>/dev/null; then
-  [$2]=yes
-else
-  echo "configure: failed program was:" >&AC_FD_CC
-  cat conftest.$ac_ext >&AC_FD_CC
-  [$2]=no
-fi
-[$3]=no
-rm -fr conftest*])dnl
 
 dnl Use the standard macros, but make them use other variable names
 dnl
-pushdef([cross_compiling], [#])dnl
 pushdef([ac_cv_prog_CXXCPP], ac_cv_build_prog_CXXCPP)dnl
 pushdef([ac_cv_prog_gxx], ac_cv_build_prog_gxx)dnl
 pushdef([ac_cv_prog_cxx_works], ac_cv_build_prog_cxx_works)dnl
@@ -70,6 +49,7 @@ pushdef([ac_cv_prog_cxx_g], ac_cv_build_prog_cxx_g)dnl
 pushdef([CXX], CXX_FOR_BUILD)dnl
 pushdef([CXXCPP], CXXCPP_FOR_BUILD)dnl
 pushdef([CXXFLAGS], CXXFLAGS_FOR_BUILD)dnl
+pushdef([CPPFLAGS], CPPFLAGS_FOR_BUILD)dnl
 pushdef([CXXCPPFLAGS], CXXCPPFLAGS_FOR_BUILD)dnl
 pushdef([host], build)dnl
 pushdef([host_alias], build_alias)dnl
@@ -84,15 +64,20 @@ pushdef([ac_cv_host_os], ac_cv_build_os)dnl
 pushdef([ac_cxxcpp], ac_build_cxxcpp)dnl
 pushdef([ac_compile], ac_build_compile)dnl
 pushdef([ac_link], ac_build_link)dnl
-pushdef([ac_tool_prefix], [#])dnl
+
+save_cross_compiling=$cross_compiling
+save_ac_tool_prefix=$ac_tool_prefix
+cross_compiling=no
+ac_tool_prefix=
 
 AC_PROG_CXX
 AC_PROG_CXXCPP
 
+ac_tool_prefix=$save_ac_tool_prefix
+cross_compiling=$save_cross_compiling
+
 dnl Restore the old definitions
 dnl
-popdef([AC_TRY_COMPILER])dnl
-popdef([ac_tool_prefix])dnl
 popdef([ac_link])dnl
 popdef([ac_compile])dnl
 popdef([ac_cxxcpp])dnl
@@ -107,14 +92,15 @@ popdef([host_cpu])dnl
 popdef([host_alias])dnl
 popdef([host])dnl
 popdef([CXXCPPFLAGS])dnl
+popdef([CPPFLAGS])dnl
 popdef([CXXFLAGS])dnl
 popdef([CXXCPP])dnl
 popdef([CXX])dnl
 popdef([ac_cv_prog_cxx_g])dnl
-popdef([ac_cv_prog_cxx_works])dnl
 popdef([ac_cv_prog_cxx_cross])dnl
+popdef([ac_cv_prog_cxx_works])dnl
 popdef([ac_cv_prog_gxx])dnl
-popdef([cross_compiling])dnl
+popdef([ac_cv_prog_CXXCPP])dnl
 
 dnl Finally, set Makefile variables
 dnl