doc: one of the fixes for an ambiguous grammar was ambiguous too

[bison.git] / configure.ac

diff --git a/configure.ac b/configure.ac
index 4cc9ef91a3c34c41f666d32fd6effd53eb8920f3..86783d525578f2dffd1400a9e8218bdd5896624f 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -72,6 +72,18 @@ if test "$enable_gcc_warnings" = yes; then
     -Wshadow -Wstrict-prototypes'
   warn_cxx='-Wnoexcept'
   AC_LANG_PUSH([C])
+  # Clang supports many of GCC's -W options, but only issues warnings
+  # on the ones it does not recognize.  In that case, gl_WARN_ADD
+  # thinks the option is supported, and unknown options are then added
+  # to CFLAGS.  But then, when -Werror is added in the test suite for
+  # instance, the warning about the unknown option turns into an
+  # error.
+  #
+  # This should be addressed by gnulib's gl_WARN_ADD, but in the
+  # meanwhile, turn warnings about unknown options into errors in
+  # CFLAGS, and restore CFLAGS after the tests.
+  save_CFLAGS=$CFLAGS
+  gl_WARN_ADD([-Werror=unknown-warning-option], [CFLAGS])
   for i in $warn_common $warn_c;
   do
     gl_WARN_ADD([$i], [WARN_CFLAGS])
@@ -80,24 +92,29 @@ if test "$enable_gcc_warnings" = yes; then
   # Warnings for the test suite only.
   gl_WARN_ADD([-Wundef], [WARN_CFLAGS_TEST])
   gl_WARN_ADD([-pedantic], [WARN_CFLAGS_TEST])
+  CFLAGS=$save_CFLAGS
   AC_LANG_POP([C])
 
   AC_LANG_PUSH([C++])
+  save_CXXFLAGS=$CXXFLAGS
+  gl_WARN_ADD([-Werror=unknown-warning-option], [CXXFLAGS])
   for i in $warn_common $warn_cxx;
   do
     gl_WARN_ADD([$i], [WARN_CXXFLAGS])
   done
-  gl_WARN_ADD([ -Wzero-as-null-pointer-constant], [WARN_CXXFLAGS],
+  gl_WARN_ADD([-Wzero-as-null-pointer-constant], [WARN_CXXFLAGS],
               [AC_LANG_PROGRAM([], [nullptr])])
   gl_WARN_ADD([-Werror], [WERROR_CXXFLAGS])
   # Warnings for the test suite only.
   gl_WARN_ADD([-Wundef], [WARN_CXXFLAGS_TEST])
   gl_WARN_ADD([-pedantic], [WARN_CXXFLAGS_TEST])
+  CXXFLAGS=$save_CXXFLAGS
   AC_LANG_POP([C++])
 fi
 
 BISON_TEST_FOR_WORKING_C_COMPILER
 BISON_TEST_FOR_WORKING_CXX_COMPILER
+BISON_C_COMPILER_POSIXLY_CORRECT
 
 AC_ARG_ENABLE([yacc],
   [AC_HELP_STRING([--disable-yacc],