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Add configure test to see if the C compiler has gcc-style computed gotos.

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We'll need this for the upcoming patch to speed up expression evaluation.
Might as well push it now to see if it behaves sanely in the buildfarm.

Andres Freund

Discussion: https://postgr.es/m/20170320062511.hp5qeurtxrwsvfxr@alap3.anarazel.de
This commit is contained in:
Tom Lane
2017-03-20 13:35:21 -04:00
parent 14a72525d2
commit bc18126a6b
5 changed files with 65 additions and 0 deletions
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24
config/c-compiler.m4
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@ -273,6 +273,30 @@ fi])# PGAC_C_BUILTIN_UNREACHABLE
# PGAC_C_COMPUTED_GOTO
# -----------------------
# Check if the C compiler knows computed gotos (gcc extension, also
# available in at least clang). If so, define HAVE_COMPUTED_GOTO.
#
# Checking whether computed gotos are supported syntax-wise ought to
# be enough, as the syntax is otherwise illegal.
AC_DEFUN([PGAC_C_COMPUTED_GOTO],
[AC_CACHE_CHECK(for computed goto support, pgac_cv_computed_goto,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
[[void *labeladdrs[] = {&&my_label};
goto *labeladdrs[0];
my_label:
return 1;
]])],
[pgac_cv_computed_goto=yes],
[pgac_cv_computed_goto=no])])
if test x"$pgac_cv_computed_goto" = xyes ; then
AC_DEFINE(HAVE_COMPUTED_GOTO, 1,
[Define to 1 if your compiler handles computed gotos.])
fi])# PGAC_C_COMPUTED_GOTO
# PGAC_C_VA_ARGS
# --------------
# Check if the C compiler understands C99-style variadic macros,