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Refactor static_assert() support.

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HAVE__STATIC_ASSERT was really a test for GCC statement expressions,
as needed for StaticAssertExpr() now that _Static_assert could be
assumed to be available through our C11 requirement.  This
artificially prevented Visual Studio from being able to use
static_assert() in other contexts.

Instead, make a new test for HAVE_STATEMENT_EXPRESSIONS, and use that
to control only whether StaticAssertExpr() uses fallback code, not the
other variants.  This improves the quality of failure messages in the
(much more common) other variants under Visual Studio.

Also get rid of the two separate implementations for C++, since the C
implementation is also also valid as C++11.  While it is a stretch to
apply HAVE_STATEMENT_EXPRESSIONS tested with $CC to a C++ compiler,
the previous C++ coding assumed that the C++ compiler had them
unconditionally, so it isn't a new stretch.  In practice, the C and
C++ compilers are very likely to agree, and if a combination is ever
reported that falsifies this assumption we can always reconsider that.

Author: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGKvr0x_oGmQTUkx%3DODgSksT2EtgCA6LmGx_jQFG%3DsDUpg%40mail.gmail.com
This commit is contained in:
Peter Eisentraut
2025-12-15 11:43:11 +01:00
parent 366dcdaf57
commit 17f446784d
6 changed files with 40 additions and 69 deletions
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26
config/c-compiler.m4
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@@ -150,23 +150,19 @@ fi])# PGAC_TYPE_128BIT_INT
# PGAC_C_STATIC_ASSERT
# --------------------
# Check if the C compiler understands _Static_assert(),
# and define HAVE__STATIC_ASSERT if so.
#
# We actually check the syntax ({ _Static_assert(...) }), because we need
# gcc-style compound expressions to be able to wrap the thing into macros.
AC_DEFUN([PGAC_C_STATIC_ASSERT],
[AC_CACHE_CHECK(for _Static_assert, pgac_cv__static_assert,
# PGAC_C_STATEMENT_EXPRESSIONS
# ----------------------------
# Check if the C compiler understands GCC statement expressions.
AC_DEFUN([PGAC_C_STATEMENT_EXPRESSIONS],
[AC_CACHE_CHECK(for statement expressions, pgac_cv_statement_expressions,
[AC_LINK_IFELSE([AC_LANG_PROGRAM([],
[({ _Static_assert(1, "foo"); })])],
[pgac_cv__static_assert=yes],
[pgac_cv__static_assert=no])])
if test x"$pgac_cv__static_assert" = xyes ; then
AC_DEFINE(HAVE__STATIC_ASSERT, 1,
[Define to 1 if your compiler understands _Static_assert.])
fi])# PGAC_C_STATIC_ASSERT
[pgac_cv_statement_expressions=yes],
[pgac_cv_statement_expressions=no])])
if test x"$pgac_cv_statement_expressions" = xyes ; then
AC_DEFINE(HAVE_STATEMENT_EXPRESSIONS, 1,
[Define to 1 if your compiler supports statement expressions.])
fi])# PGAC_C_STATEMENT_EXPRESSIONS