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Require sizeof(bool) == 1.

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The C standard says that sizeof(bool) is implementation-defined, but we
know of no current systems where it is not 1.  The last known systems
seem to have been Apple macOS/PowerPC 10.5 and Microsoft Visual C++ 4,
both long defunct.

PostgreSQL has always required sizeof(bool) == 1 for the definition of
bool that it used, but previously it would define its own type if the
system-provided bool had a different size.  That was liable to cause
memory layout problems when interacting with system and third-party
libraries on (by now hypothetical) computers with wider _Bool, and now
C23 has introduced a new problem by making bool a built-in datatype
(like C++), so the fallback code doesn't even compile.  We could
probably work around that, but then we'd be writing new untested code
for a computer that doesn't exist.

Instead, delete the unreachable and C23-uncompilable fallback code, and
let existing static assertions fail if the system-provided bool is too
wide.  If we ever get a problem report from a real system, then it will
be time to figure out what to do about it in a way that also works on
modern compilers.

Note on C++: Previously we avoided including <stdbool.h> or trying to
define a new bool type in headers that might be included by C++ code.
These days we might as well just include <stdbool.h> unconditionally:
it should be visible to C++11 but do nothing, just as in C23.  We
already include <stdint.h> without C++ guards in c.h, and that falls
under the same C99-compatibility section of the C++11 standard as
<stdbool.h>, so let's remove the guards here too.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/3198438.1731895163%40sss.pgh.pa.us
This commit is contained in:
Thomas Munro
2024-11-28 11:48:07 +13:00
parent 4b03a27faf
commit 97525bc5c8
11 changed files with 8 additions and 160 deletions
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41
configure vendored
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@ -14958,47 +14958,6 @@ if test "$ac_cv_sizeof_off_t" -lt 8; then
fi
fi
# The cast to long int works around a bug in the HP C Compiler
# version HP92453-01 B.11.11.23709.GP, which incorrectly rejects
# declarations like `int a3[[(sizeof (unsigned char)) >= 0]];'.
# This bug is HP SR number 8606223364.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking size of bool" >&5
$as_echo_n "checking size of bool... " >&6; }
if ${ac_cv_sizeof_bool+:} false; then :
$as_echo_n "(cached) " >&6
else
if ac_fn_c_compute_int "$LINENO" "(long int) (sizeof (bool))" "ac_cv_sizeof_bool" "#include <stdbool.h>
"; then :
else
if test "$ac_cv_type_bool" = yes; then
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
as_fn_error 77 "cannot compute sizeof (bool)
See \`config.log' for more details" "$LINENO" 5; }
else
ac_cv_sizeof_bool=0
fi
fi
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_sizeof_bool" >&5
$as_echo "$ac_cv_sizeof_bool" >&6; }
cat >>confdefs.h <<_ACEOF
#define SIZEOF_BOOL $ac_cv_sizeof_bool
_ACEOF
if test "$ac_cv_sizeof_bool" = 1; then
$as_echo "#define PG_USE_STDBOOL 1" >>confdefs.h
fi
##
## Functions, global variables