GCC 12 complains that set_stack_base is storing the address of
a local variable in a long-lived pointer. This is an entirely
reasonable warning (indeed, it just helped us find a bug);
but that behavior is intentional here. We can work around it
by using __builtin_frame_address(0) instead of a specific local
variable; that produces an address a dozen or so bytes different,
in my testing, but we don't care about such a small difference.
Maybe someday a compiler lacking that function will start to issue
a similar warning, but we'll worry about that when it happens.
Patch by me, per a suggestion from Andres Freund. Back-patch to
v12, which is as far back as the patch will go without some pain.
(Recently-established project policy would permit a back-patch as
far as 9.2, but I'm disinclined to expend the work until GCC 12
is much more widespread.)
Discussion: https://postgr.es/m/
3773792.
1645141467@sss.pgh.pa.us
+# PGAC_CHECK_BUILTIN_FUNC_PTR
+# -----------------------
+# Like PGAC_CHECK_BUILTIN_FUNC, except that the function is assumed to
+# return a pointer type, and the argument(s) should be given literally.
+# This handles some cases that PGAC_CHECK_BUILTIN_FUNC doesn't.
+AC_DEFUN([PGAC_CHECK_BUILTIN_FUNC_PTR],
+[AC_CACHE_CHECK(for $1, pgac_cv$1,
+[AC_LINK_IFELSE([AC_LANG_PROGRAM([
+void *
+call$1(void)
+{
+ return $1($2);
+}], [])],
+[pgac_cv$1=yes],
+[pgac_cv$1=no])])
+if test x"${pgac_cv$1}" = xyes ; then
+AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE$1]), 1,
+ [Define to 1 if your compiler understands $1.])
+fi])# PGAC_CHECK_BUILTIN_FUNC_PTR
+
+
+
# PGAC_PROG_VARCC_VARFLAGS_OPT
# ----------------------------
# Given a compiler, variable name and a string, check if the compiler
#define HAVE__BUILTIN_POPCOUNT 1
_ACEOF
+fi
+# __builtin_frame_address may draw a diagnostic for non-constant argument,
+# so it needs a different test function.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_frame_address" >&5
+$as_echo_n "checking for __builtin_frame_address... " >&6; }
+if ${pgac_cv__builtin_frame_address+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+void *
+call__builtin_frame_address(void)
+{
+ return __builtin_frame_address(0);
+}
+int
+main ()
+{
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+ pgac_cv__builtin_frame_address=yes
+else
+ pgac_cv__builtin_frame_address=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+ conftest$ac_exeext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__builtin_frame_address" >&5
+$as_echo "$pgac_cv__builtin_frame_address" >&6; }
+if test x"${pgac_cv__builtin_frame_address}" = xyes ; then
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE__BUILTIN_FRAME_ADDRESS 1
+_ACEOF
+
fi
# We require 64-bit fseeko() to be available, but run this check anyway
PGAC_CHECK_BUILTIN_FUNC([__builtin_clz], [unsigned int x])
PGAC_CHECK_BUILTIN_FUNC([__builtin_ctz], [unsigned int x])
PGAC_CHECK_BUILTIN_FUNC([__builtin_popcount], [unsigned int x])
+# __builtin_frame_address may draw a diagnostic for non-constant argument,
+# so it needs a different test function.
+PGAC_CHECK_BUILTIN_FUNC_PTR([__builtin_frame_address], [0])
# We require 64-bit fseeko() to be available, but run this check anyway
# in case it finds that _LARGEFILE_SOURCE has to be #define'd for that.
/*
* Set reference point for stack-depth checking.
*/
- set_stack_base();
+ (void) set_stack_base();
/*
* Initialize pipe (or process handle on Windows) that allows children to
pg_stack_base_t
set_stack_base(void)
{
+#ifndef HAVE__BUILTIN_FRAME_ADDRESS
char stack_base;
+#endif
pg_stack_base_t old;
#if defined(__ia64__) || defined(__ia64)
old = stack_base_ptr;
#endif
- /* Set up reference point for stack depth checking */
+ /*
+ * Set up reference point for stack depth checking. On recent gcc we use
+ * __builtin_frame_address() to avoid a warning about storing a local
+ * variable's address in a long-lived variable.
+ */
+#ifdef HAVE__BUILTIN_FRAME_ADDRESS
+ stack_base_ptr = __builtin_frame_address(0);
+#else
stack_base_ptr = &stack_base;
+#endif
#if defined(__ia64__) || defined(__ia64)
register_stack_base_ptr = ia64_get_bsp();
#endif
IsUnderPostmaster = true; /* we are a postmaster subprocess now */
/*
- * Set reference point for stack-depth checking. We re-do that even in the
- * !EXEC_BACKEND case, because there are some edge cases where processes
- * are started with an alternative stack (e.g. starting bgworkers when
- * running postgres using the rr debugger, as bgworkers are launched from
- * signal handlers).
+ * Set reference point for stack-depth checking. This might seem
+ * redundant in !EXEC_BACKEND builds; but it's not because the postmaster
+ * launches its children from signal handlers, so we might be running on
+ * an alternative stack.
*/
- set_stack_base();
+ (void) set_stack_base();
InitProcessGlobals();
/* Define to 1 if your compiler understands __builtin_ctz. */
#undef HAVE__BUILTIN_CTZ
+/* Define to 1 if your compiler understands __builtin_frame_address. */
+#undef HAVE__BUILTIN_FRAME_ADDRESS
+
/* Define to 1 if your compiler understands __builtin_$op_overflow. */
#undef HAVE__BUILTIN_OP_OVERFLOW
HAVE__BUILTIN_CLZ => undef,
HAVE__BUILTIN_CONSTANT_P => undef,
HAVE__BUILTIN_CTZ => undef,
+ HAVE__BUILTIN_FRAME_ADDRESS => undef,
HAVE__BUILTIN_OP_OVERFLOW => undef,
HAVE__BUILTIN_POPCOUNT => undef,
HAVE__BUILTIN_TYPES_COMPATIBLE_P => undef,
projects / postgresql.git / commitdiff