Suppress warning about stack_base_ptr with late-model GCC.
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
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@ -381,6 +381,28 @@ fi])# PGAC_CHECK_BUILTIN_FUNC
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# PGAC_CHECK_BUILTIN_FUNC_PTR
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# -----------------------
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# Like PGAC_CHECK_BUILTIN_FUNC, except that the function is assumed to
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# return a pointer type, and the argument(s) should be given literally.
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# This handles some cases that PGAC_CHECK_BUILTIN_FUNC doesn't.
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AC_DEFUN([PGAC_CHECK_BUILTIN_FUNC_PTR],
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[AC_CACHE_CHECK(for $1, pgac_cv$1,
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[AC_LINK_IFELSE([AC_LANG_PROGRAM([
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void *
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call$1(void)
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{
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return $1($2);
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}], [])],
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[pgac_cv$1=yes],
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[pgac_cv$1=no])])
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if test x"${pgac_cv$1}" = xyes ; then
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AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE$1]), 1,
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[Define to 1 if your compiler understands $1.])
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fi])# PGAC_CHECK_BUILTIN_FUNC_PTR
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# PGAC_PROG_VARCC_VARFLAGS_OPT
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# ----------------------------
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# Given a compiler, variable name and a string, check if the compiler
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@ -15944,6 +15944,46 @@ cat >>confdefs.h <<_ACEOF
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#define HAVE__BUILTIN_POPCOUNT 1
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_ACEOF
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fi
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# __builtin_frame_address may draw a diagnostic for non-constant argument,
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# so it needs a different test function.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_frame_address" >&5
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$as_echo_n "checking for __builtin_frame_address... " >&6; }
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if ${pgac_cv__builtin_frame_address+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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void *
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call__builtin_frame_address(void)
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{
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return __builtin_frame_address(0);
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}
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int
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main ()
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{
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;
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return 0;
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}
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_ACEOF
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if ac_fn_c_try_link "$LINENO"; then :
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pgac_cv__builtin_frame_address=yes
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else
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pgac_cv__builtin_frame_address=no
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fi
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rm -f core conftest.err conftest.$ac_objext \
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conftest$ac_exeext conftest.$ac_ext
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__builtin_frame_address" >&5
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$as_echo "$pgac_cv__builtin_frame_address" >&6; }
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if test x"${pgac_cv__builtin_frame_address}" = xyes ; then
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cat >>confdefs.h <<_ACEOF
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#define HAVE__BUILTIN_FRAME_ADDRESS 1
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_ACEOF
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fi
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# We require 64-bit fseeko() to be available, but run this check anyway
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@ -1776,6 +1776,9 @@ PGAC_CHECK_BUILTIN_FUNC([__builtin_bswap64], [long int x])
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PGAC_CHECK_BUILTIN_FUNC([__builtin_clz], [unsigned int x])
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PGAC_CHECK_BUILTIN_FUNC([__builtin_ctz], [unsigned int x])
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PGAC_CHECK_BUILTIN_FUNC([__builtin_popcount], [unsigned int x])
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# __builtin_frame_address may draw a diagnostic for non-constant argument,
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# so it needs a different test function.
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PGAC_CHECK_BUILTIN_FUNC_PTR([__builtin_frame_address], [0])
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# We require 64-bit fseeko() to be available, but run this check anyway
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# in case it finds that _LARGEFILE_SOURCE has to be #define'd for that.
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@ -1083,7 +1083,7 @@ PostmasterMain(int argc, char *argv[])
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/*
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* Set reference point for stack-depth checking.
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*/
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set_stack_base();
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(void) set_stack_base();
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/*
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* Initialize pipe (or process handle on Windows) that allows children to
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@ -129,17 +129,15 @@ static long max_stack_depth_bytes = 100 * 1024L;
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/*
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* Stack base pointer -- initialized by PostmasterMain and inherited by
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* subprocesses. This is not static because old versions of PL/Java modify
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* it directly. Newer versions use set_stack_base(), but we want to stay
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* binary-compatible for the time being.
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* subprocesses (but see also InitPostmasterChild).
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*/
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char *stack_base_ptr = NULL;
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static char *stack_base_ptr = NULL;
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/*
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* On IA64 we also have to remember the register stack base.
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*/
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#if defined(__ia64__) || defined(__ia64)
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char *register_stack_base_ptr = NULL;
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static char *register_stack_base_ptr = NULL;
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#endif
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/*
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pg_stack_base_t
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set_stack_base(void)
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{
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#ifndef HAVE__BUILTIN_FRAME_ADDRESS
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char stack_base;
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#endif
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pg_stack_base_t old;
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#if defined(__ia64__) || defined(__ia64)
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old = stack_base_ptr;
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#endif
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/* Set up reference point for stack depth checking */
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/*
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* Set up reference point for stack depth checking. On recent gcc we use
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* __builtin_frame_address() to avoid a warning about storing a local
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* variable's address in a long-lived variable.
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*/
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#ifdef HAVE__BUILTIN_FRAME_ADDRESS
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stack_base_ptr = __builtin_frame_address(0);
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#else
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stack_base_ptr = &stack_base;
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#endif
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#if defined(__ia64__) || defined(__ia64)
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register_stack_base_ptr = ia64_get_bsp();
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#endif
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@ -106,13 +106,12 @@ InitPostmasterChild(void)
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#endif
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/*
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* Set reference point for stack-depth checking. We re-do that even in the
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* !EXEC_BACKEND case, because there are some edge cases where processes
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* are started with an alternative stack (e.g. starting bgworkers when
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* running postgres using the rr debugger, as bgworkers are launched from
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* signal handlers).
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* Set reference point for stack-depth checking. This might seem
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* redundant in !EXEC_BACKEND builds; but it's not because the postmaster
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* launches its children from signal handlers, so we might be running on
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* an alternative stack.
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*/
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set_stack_base();
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(void) set_stack_base();
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InitProcessGlobals();
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@ -739,6 +739,9 @@
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/* Define to 1 if your compiler understands __builtin_ctz. */
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#undef HAVE__BUILTIN_CTZ
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/* Define to 1 if your compiler understands __builtin_frame_address. */
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#undef HAVE__BUILTIN_FRAME_ADDRESS
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/* Define to 1 if your compiler understands __builtin_$op_overflow. */
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#undef HAVE__BUILTIN_OP_OVERFLOW
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@ -439,6 +439,7 @@ sub GenerateFiles
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HAVE__BUILTIN_CLZ => undef,
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HAVE__BUILTIN_CONSTANT_P => undef,
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HAVE__BUILTIN_CTZ => undef,
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HAVE__BUILTIN_FRAME_ADDRESS => undef,
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HAVE__BUILTIN_OP_OVERFLOW => undef,
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HAVE__BUILTIN_POPCOUNT => undef,
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HAVE__BUILTIN_TYPES_COMPATIBLE_P => undef,
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