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b853eb9718
In commit 71450d7fd6, we added code to inform
suitably-intelligent compilers that ereport() doesn't return if the elevel
is ERROR or higher. This patch extends that to elog(), and also fixes a
double-evaluation hazard that the previous commit created in ereport(),
as well as reducing the emitted code size.
The elog() improvement requires the compiler to support __VA_ARGS__, which
should be available in just about anything nowadays since it's required by
C99. But our minimum language baseline is still C89, so add a configure
test for that.
The previous commit assumed that ereport's elevel could be evaluated twice,
which isn't terribly safe --- there are already counterexamples in xlog.c.
On compilers that have __builtin_constant_p, we can use that to protect the
second test, since there's no possible optimization gain if the compiler
doesn't know the value of elevel. Otherwise, use a local variable inside
the macros to prevent double evaluation. The local-variable solution is
inferior because (a) it leads to useless code being emitted when elevel
isn't constant, and (b) it increases the optimization level needed for the
compiler to recognize that subsequent code is unreachable. But it seems
better than not teaching non-gcc compilers about unreachability at all.
Lastly, if the compiler has __builtin_unreachable(), we can use that
instead of abort(), resulting in a noticeable code savings since no
function call is actually emitted. However, it seems wise to do this only
in non-assert builds. In an assert build, continue to use abort(), so that
the behavior will be predictable and debuggable if the "impossible"
happens.
These changes involve making the ereport and elog macros emit do-while
statement blocks not just expressions, which forces small changes in
a few call sites.
Andres Freund, Tom Lane, Heikki Linnakangas
267 lines
8.8 KiB
Plaintext
267 lines
8.8 KiB
Plaintext
# Macros to detect C compiler features
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# config/c-compiler.m4
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# PGAC_C_SIGNED
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# -------------
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# Check if the C compiler understands signed types.
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AC_DEFUN([PGAC_C_SIGNED],
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[AC_CACHE_CHECK(for signed types, pgac_cv_c_signed,
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[AC_TRY_COMPILE([],
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[signed char c; signed short s; signed int i;],
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[pgac_cv_c_signed=yes],
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[pgac_cv_c_signed=no])])
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if test x"$pgac_cv_c_signed" = xno ; then
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AC_DEFINE(signed,, [Define to empty if the C compiler does not understand signed types.])
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fi])# PGAC_C_SIGNED
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# PGAC_C_INLINE
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# -------------
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# Check if the C compiler understands inline functions.
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# Defines: inline, PG_USE_INLINE
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AC_DEFUN([PGAC_C_INLINE],
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[AC_C_INLINE
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AC_CACHE_CHECK([for quiet inline (no complaint if unreferenced)], pgac_cv_c_inline_quietly,
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[pgac_cv_c_inline_quietly=no
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if test "$ac_cv_c_inline" != no; then
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pgac_c_inline_save_werror=$ac_c_werror_flag
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ac_c_werror_flag=yes
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AC_LINK_IFELSE([AC_LANG_PROGRAM([static inline int fun () {return 0;}],[])],
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[pgac_cv_c_inline_quietly=yes])
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ac_c_werror_flag=$pgac_c_inline_save_werror
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fi])
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if test "$pgac_cv_c_inline_quietly" != no; then
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AC_DEFINE_UNQUOTED([PG_USE_INLINE], 1,
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[Define to 1 if "static inline" works without unwanted warnings from ]
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[compilations where static inline functions are defined but not called.])
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fi
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])# PGAC_C_INLINE
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# PGAC_TYPE_64BIT_INT(TYPE)
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# -------------------------
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# Check if TYPE is a working 64 bit integer type. Set HAVE_TYPE_64 to
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# yes or no respectively, and define HAVE_TYPE_64 if yes.
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AC_DEFUN([PGAC_TYPE_64BIT_INT],
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[define([Ac_define], [translit([have_$1_64], [a-z *], [A-Z_P])])dnl
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define([Ac_cachevar], [translit([pgac_cv_type_$1_64], [ *], [_p])])dnl
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AC_CACHE_CHECK([whether $1 is 64 bits], [Ac_cachevar],
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[AC_TRY_RUN(
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[typedef $1 ac_int64;
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/*
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* These are globals to discourage the compiler from folding all the
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* arithmetic tests down to compile-time constants.
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*/
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ac_int64 a = 20000001;
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ac_int64 b = 40000005;
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int does_int64_work()
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{
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ac_int64 c,d;
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if (sizeof(ac_int64) != 8)
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return 0; /* definitely not the right size */
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/* Do perfunctory checks to see if 64-bit arithmetic seems to work */
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c = a * b;
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d = (c + b) / b;
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if (d != a+1)
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return 0;
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return 1;
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}
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main() {
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exit(! does_int64_work());
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}],
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[Ac_cachevar=yes],
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[Ac_cachevar=no],
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[# If cross-compiling, check the size reported by the compiler and
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# trust that the arithmetic works.
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AC_COMPILE_IFELSE([AC_LANG_BOOL_COMPILE_TRY([], [sizeof($1) == 8])],
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Ac_cachevar=yes,
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Ac_cachevar=no)])])
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Ac_define=$Ac_cachevar
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if test x"$Ac_cachevar" = xyes ; then
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AC_DEFINE(Ac_define, 1, [Define to 1 if `]$1[' works and is 64 bits.])
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fi
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undefine([Ac_define])dnl
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undefine([Ac_cachevar])dnl
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])# PGAC_TYPE_64BIT_INT
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# PGAC_C_FUNCNAME_SUPPORT
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# -----------------------
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# Check if the C compiler understands __func__ (C99) or __FUNCTION__ (gcc).
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# Define HAVE_FUNCNAME__FUNC or HAVE_FUNCNAME__FUNCTION accordingly.
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AC_DEFUN([PGAC_C_FUNCNAME_SUPPORT],
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[AC_CACHE_CHECK(for __func__, pgac_cv_funcname_func_support,
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[AC_TRY_COMPILE([#include <stdio.h>],
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[printf("%s\n", __func__);],
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[pgac_cv_funcname_func_support=yes],
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[pgac_cv_funcname_func_support=no])])
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if test x"$pgac_cv_funcname_func_support" = xyes ; then
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AC_DEFINE(HAVE_FUNCNAME__FUNC, 1,
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[Define to 1 if your compiler understands __func__.])
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else
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AC_CACHE_CHECK(for __FUNCTION__, pgac_cv_funcname_function_support,
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[AC_TRY_COMPILE([#include <stdio.h>],
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[printf("%s\n", __FUNCTION__);],
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[pgac_cv_funcname_function_support=yes],
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[pgac_cv_funcname_function_support=no])])
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if test x"$pgac_cv_funcname_function_support" = xyes ; then
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AC_DEFINE(HAVE_FUNCNAME__FUNCTION, 1,
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[Define to 1 if your compiler understands __FUNCTION__.])
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fi
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fi])# PGAC_C_FUNCNAME_SUPPORT
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# PGAC_C_STATIC_ASSERT
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# --------------------
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# Check if the C compiler understands _Static_assert(),
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# and define HAVE__STATIC_ASSERT if so.
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#
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# We actually check the syntax ({ _Static_assert(...) }), because we need
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# gcc-style compound expressions to be able to wrap the thing into macros.
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AC_DEFUN([PGAC_C_STATIC_ASSERT],
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[AC_CACHE_CHECK(for _Static_assert, pgac_cv__static_assert,
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[AC_TRY_LINK([],
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[({ _Static_assert(1, "foo"); })],
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[pgac_cv__static_assert=yes],
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[pgac_cv__static_assert=no])])
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if test x"$pgac_cv__static_assert" = xyes ; then
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AC_DEFINE(HAVE__STATIC_ASSERT, 1,
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[Define to 1 if your compiler understands _Static_assert.])
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fi])# PGAC_C_STATIC_ASSERT
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# PGAC_C_TYPES_COMPATIBLE
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# -----------------------
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# Check if the C compiler understands __builtin_types_compatible_p,
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# and define HAVE__BUILTIN_TYPES_COMPATIBLE_P if so.
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#
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# We check usage with __typeof__, though it's unlikely any compiler would
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# have the former and not the latter.
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AC_DEFUN([PGAC_C_TYPES_COMPATIBLE],
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[AC_CACHE_CHECK(for __builtin_types_compatible_p, pgac_cv__types_compatible,
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[AC_TRY_COMPILE([],
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[ int x; static int y[__builtin_types_compatible_p(__typeof__(x), int)]; ],
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[pgac_cv__types_compatible=yes],
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[pgac_cv__types_compatible=no])])
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if test x"$pgac_cv__types_compatible" = xyes ; then
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AC_DEFINE(HAVE__BUILTIN_TYPES_COMPATIBLE_P, 1,
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[Define to 1 if your compiler understands __builtin_types_compatible_p.])
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fi])# PGAC_C_TYPES_COMPATIBLE
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# PGAC_C_BUILTIN_CONSTANT_P
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# -------------------------
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# Check if the C compiler understands __builtin_constant_p(),
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# and define HAVE__BUILTIN_CONSTANT_P if so.
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AC_DEFUN([PGAC_C_BUILTIN_CONSTANT_P],
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[AC_CACHE_CHECK(for __builtin_constant_p, pgac_cv__builtin_constant_p,
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[AC_TRY_COMPILE([static int x; static int y[__builtin_constant_p(x) ? x : 1];],
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[],
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[pgac_cv__builtin_constant_p=yes],
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[pgac_cv__builtin_constant_p=no])])
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if test x"$pgac_cv__builtin_constant_p" = xyes ; then
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AC_DEFINE(HAVE__BUILTIN_CONSTANT_P, 1,
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[Define to 1 if your compiler understands __builtin_constant_p.])
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fi])# PGAC_C_BUILTIN_CONSTANT_P
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# PGAC_C_BUILTIN_UNREACHABLE
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# --------------------------
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# Check if the C compiler understands __builtin_unreachable(),
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# and define HAVE__BUILTIN_UNREACHABLE if so.
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#
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# NB: Don't get the idea of putting a for(;;); or such before the
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# __builtin_unreachable() call. Some compilers would remove it before linking
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# and only a warning instead of an error would be produced.
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AC_DEFUN([PGAC_C_BUILTIN_UNREACHABLE],
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[AC_CACHE_CHECK(for __builtin_unreachable, pgac_cv__builtin_unreachable,
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[AC_TRY_LINK([],
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[__builtin_unreachable();],
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[pgac_cv__builtin_unreachable=yes],
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[pgac_cv__builtin_unreachable=no])])
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if test x"$pgac_cv__builtin_unreachable" = xyes ; then
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AC_DEFINE(HAVE__BUILTIN_UNREACHABLE, 1,
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[Define to 1 if your compiler understands __builtin_unreachable.])
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fi])# PGAC_C_BUILTIN_UNREACHABLE
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# PGAC_C_VA_ARGS
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# --------------
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# Check if the C compiler understands C99-style variadic macros,
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# and define HAVE__VA_ARGS if so.
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AC_DEFUN([PGAC_C_VA_ARGS],
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[AC_CACHE_CHECK(for __VA_ARGS__, pgac_cv__va_args,
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[AC_TRY_COMPILE([#include <stdio.h>],
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[#define debug(...) fprintf(stderr, __VA_ARGS__)
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debug("%s", "blarg");
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],
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[pgac_cv__va_args=yes],
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[pgac_cv__va_args=no])])
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if test x"$pgac_cv__va_args" = xyes ; then
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AC_DEFINE(HAVE__VA_ARGS, 1,
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[Define to 1 if your compiler understands __VA_ARGS__ in macros.])
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fi])# PGAC_C_VA_ARGS
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# PGAC_PROG_CC_CFLAGS_OPT
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# -----------------------
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# Given a string, check if the compiler supports the string as a
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# command-line option. If it does, add the string to CFLAGS.
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AC_DEFUN([PGAC_PROG_CC_CFLAGS_OPT],
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[define([Ac_cachevar], [AS_TR_SH([pgac_cv_prog_cc_cflags_$1])])dnl
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AC_CACHE_CHECK([whether $CC supports $1], [Ac_cachevar],
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[pgac_save_CFLAGS=$CFLAGS
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CFLAGS="$pgac_save_CFLAGS $1"
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ac_save_c_werror_flag=$ac_c_werror_flag
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ac_c_werror_flag=yes
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_AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
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[Ac_cachevar=yes],
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[Ac_cachevar=no])
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ac_c_werror_flag=$ac_save_c_werror_flag
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CFLAGS="$pgac_save_CFLAGS"])
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if test x"$Ac_cachevar" = x"yes"; then
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CFLAGS="$CFLAGS $1"
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fi
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undefine([Ac_cachevar])dnl
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])# PGAC_PROG_CC_CFLAGS_OPT
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# PGAC_PROG_CC_LDFLAGS_OPT
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# ------------------------
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# Given a string, check if the compiler supports the string as a
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# command-line option. If it does, add the string to LDFLAGS.
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# For reasons you'd really rather not know about, this checks whether
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# you can link to a particular function, not just whether you can link.
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# In fact, we must actually check that the resulting program runs :-(
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AC_DEFUN([PGAC_PROG_CC_LDFLAGS_OPT],
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[define([Ac_cachevar], [AS_TR_SH([pgac_cv_prog_cc_ldflags_$1])])dnl
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AC_CACHE_CHECK([whether $CC supports $1], [Ac_cachevar],
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[pgac_save_LDFLAGS=$LDFLAGS
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LDFLAGS="$pgac_save_LDFLAGS $1"
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AC_RUN_IFELSE([AC_LANG_PROGRAM([extern void $2 (); void (*fptr) () = $2;],[])],
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[Ac_cachevar=yes],
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[Ac_cachevar=no],
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[Ac_cachevar="assuming no"])
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LDFLAGS="$pgac_save_LDFLAGS"])
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if test x"$Ac_cachevar" = x"yes"; then
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LDFLAGS="$LDFLAGS $1"
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fi
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undefine([Ac_cachevar])dnl
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])# PGAC_PROG_CC_LDFLAGS_OPT
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