Previously, c.h made <assert.h> only available in frontends (#ifdef
FRONTEND), which was probably reasonable, because the only thing it
would give you is assert(), which you generally shouldn't use in the
backend. But with C11, <assert.h> also makes available
static_assert(), which would be useful everywhere. So this patch
moves <assert.h> to the commonly available header files in c.h and
fixes a small complication in regcustom.h that resulted from that.
Co-authored-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA%2BhUKGKvr0x_oGmQTUkx%3DODgSksT2EtgCA6LmGx_jQFG%3DsDUpg%40mail.gmail.com
Although clang claims to be compatible with gcc's printf format
archetypes, this appears to be a falsehood: it likes __syslog__
(which gcc does not, on most platforms) and doesn't accept
gnu_printf. This means that if you try to use gcc with clang++
or clang with g++, you get compiler warnings when compiling
printf-like calls in our C++ code. This has been true for quite
awhile, but it's gotten more annoying with the recent appearance
of several buildfarm members that are configured like this.
To fix, run separate probes for the format archetype to use with the
C and C++ compilers, and conditionally define PG_PRINTF_ATTRIBUTE
depending on __cplusplus.
(We could alternatively insist that you not mix-and-match C and
C++ compilers; but if the case works otherwise, this is a poor
reason to insist on that.)
No back-patch for now, but we may want to do that if this
patch survives buildfarm testing.
Discussion: https://postgr.es/m/986485.1764825548@sss.pgh.pa.us
This eliminates MultiXactOffset wraparound and the 2^32 limit on the
total number of multixid members. Multixids are still limited to 2^31,
but this is a nice improvement because 'members' can grow much faster
than the number of multixids. On such systems, you can now run longer
before hitting hard limits or triggering anti-wraparound vacuums.
Not having to deal with MultiXactOffset wraparound also simplifies the
code and removes some gnarly corner cases.
We no longer need to perform emergency anti-wraparound freezing
because of running out of 'members' space, so the offset stop limit is
gone. But you might still not want 'members' to consume huge amounts
of disk space. For that reason, I kept the logic for lowering vacuum's
multixid freezing cutoff if a large amount of 'members' space is
used. The thresholds for that are roughly the same as the "safe" and
"danger" thresholds used before, 2 billion transactions and 4 billion
transactions. This keeps the behavior for the freeze cutoff roughly
the same as before. It might make sense to make this smarter or
configurable, now that the threshold is only needed to manage disk
usage, but that's left for the future.
Add code to pg_upgrade to convert multitransactions from the old to
the new format, rewriting the pg_multixact SLRU files. Because
pg_upgrade now rewrites the files, we can get rid of some hacks we had
put in place to deal with old bugs and upgraded clusters. Bump catalog
version for the pg_multixact/offsets format change.
Author: Maxim Orlov <orlovmg@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com>
Discussion: https://www.postgresql.org/message-id/CACG%3DezaWg7_nt-8ey4aKv2w9LcuLthHknwCawmBgEeTnJrJTcw@mail.gmail.com
The comment for the Pointer type said 'XXX Pointer arithmetic is done
with this, so it can't be void * under "true" ANSI compilers.'. This
has been fixed in the previous commit 756a436893. This now changes
the definition of the type from char * to void *, as envisaged by that
comment.
Extension code that relies on using Pointer for pointer arithmetic
will need to make changes similar to commit 756a436893, but those
changes would be backward compatible.
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://www.postgresql.org/message-id/4154950a-47ae-4223-bd01-1235cc50e933%40eisentraut.org
This replaces some uses of pg_attribute_aligned() with the standard
alignas() for cases where extended alignment (larger than max_align_t)
is required.
This patch stipulates that all supported compilers must support
alignments up to PG_IO_ALIGN_SIZE, but that seems pretty likely.
We can then also desupport the case where direct I/O is disabled
because pg_attribute_aligned is not supported.
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/46f05236-d4d4-4b4e-84d4-faa500f14691%40eisentraut.org
This changes a few union members that only existed to ensure
alignments and replaces them with the C11 alignas specifier.
This change only uses fundamental alignments (meaning approximately
alignments of basic types), which all C11 compilers must support.
There are opportunities for similar changes using extended alignments,
for example in PGIOAlignedBlock, but these are not necessarily
supported by all compilers, so they are kept as a separate change.
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/46f05236-d4d4-4b4e-84d4-faa500f14691%40eisentraut.org
Likewise for MemSetAligned.
"long" wasn't the most suitable type for these macros as with MSVC in
64-bit builds, sizeof(long) == 4, which is narrower than the processor's
word size, therefore these macros had to perform twice as many loops as
they otherwise might.
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/CAApHDvoGFjSA3aNyVQ3ivbyc4ST=CC5L-_VjEUQ92HbE2Cxovg@mail.gmail.com
MSVC in C11 mode supports the standard restrict qualifier, so we don't
need the workaround naming pg_restrict anymore.
Even though restrict is in C99 and should be supported by all
supported compilers, we keep the configure test and the hardcoded
redirection to __restrict, because that will also work in C++ in all
supported compilers. (restrict is not part of the C++ standard.)
For backward compatibility for extensions, we keep a #define of
pg_restrict around, but our own code doesn't use it anymore.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/0e3d8644-c01d-4374-86ea-9f0a987981f0%40eisentraut.org
It had always been intended that this already works correctly as
pg_unreachable() uses __assume(0) on MSVC, and that directs the compiler
in a way so it knows that a given function won't return. However, with
ereport_domain(), it didn't work...
It's now understood that the failure to determine that elog(ERROR) does not
return comes from the inability of the MSVC compiler to detect the "const
int elevel_" is the same as the "elevel" macro parameter. MSVC seems to be
unable to make the "if (elevel_ >= ERROR) branch constantly-true when the
macro is used with any elevel >= ERROR, therefore the pg_unreachable() is
seen to only be present in a *conditional* branch rather than present
*unconditionally*.
While there seems to be no way to force the compiler into knowing that
elevel_ is equal to elevel within the ereport_domain() macro, there is a
way in C11 to determine if the elevel parameter is a compile-time
constant or not. This is done via some hackery using the _Generic()
intrinsic function, which gives us functionality similar to GCC's
__builtin_constant_p(), albeit only for integers.
Here we define pg_builtin_integer_constant_p() for this purpose.
Callers can check for availability via HAVE_PG_BUILTIN_INTEGER_CONSTANT_P.
ereport_domain() has been adjusted to use
pg_builtin_integer_constant_p() instead of __builtin_constant_p().
It's not quite clear at this stage if this now allows us to forego doing
the likes of "return NULL; /* keep compiler quiet */" as there may be other
compilers in use that have similar struggles. It's just a matter of time
before someone commits a function that does not "return" a value after
an elog(ERROR). Let's make time and lack of complaints about said commit
be the judge of if we need to continue the "/* keep compiler quiet */"
palaver.
Author: David Rowley <drowleyml@gmail.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/CAApHDvom02B_XNVSkvxznVUyZbjGAR+5myA89ZcbEd3=PA9UcA@mail.gmail.com
Per discussion, this compiler suite is no longer maintained, and
it has not been able to compile PostgreSQL since at least PostgreSQL
17.
This removes all the remaining support code for this compiler.
Note that the Solaris operating system continues to be supported, but
using GCC as the compiler.
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/a0f817ee-fb86-483a-8a14-b6f7f5991b6e%40eisentraut.org
Remove conditionally-compiled code for the other case.
Replace uses of FLOAT8PASSBYVAL with constant "true", mainly because
it was quite confusing in cases where the type we were dealing with
wasn't float8.
I left the associated pg_control and Pg_magic_struct fields in place.
Perhaps we should get rid of them, but it would save little, so it
doesn't seem worth thinking hard about the compatibility implications.
I just labeled them "vestigial" in places where that seemed helpful.
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/1749799.1752797397@sss.pgh.pa.us
These were introduced (commit efdc7d7475) at the same time as we were
moving to using the standard inttypes.h format macros (commit
a0ed19e0a9). It doesn't seem useful to keep a new already-deprecated
interface like this with only a few users, so remove the new symbols
again and have the callers use PRIx64.
(Also, INT64_HEX_FORMAT was kind of a misnomer, since hex formats all
use unsigned types.)
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/0ac47b5d-e5ab-4cac-98a7-bdee0e2831e4%40eisentraut.org
Switch MSVC to use the conforming preprocessor, using the
/Zc:preprocessor option.
This allows us to drop the alternative implementation of
VA_ARGS_NARGS() for the previous "traditional" preprocessor.
This also prepares the way for enabling C11 mode in the future, which
enables the conforming preprocessor by default.
This now requires Visual Studio 2019. The installation documentation
is adjusted accordingly.
Discussion: https://www.postgresql.org/message-id/flat/01a69441-af54-4822-891b-ca28e05b215a%40eisentraut.org
When pg_nodiscard was first added, the C standard draft had it as a
function specifier, and so the code comment about placement was
written with that in mind. The final C23 standard has it as an
attribute and the placement rules are a bit different for that.
Specifically, it needs to be before extern or static. (Or at least
both current clang and gcc require that.) So just swap these. (To be
clear: The current implementation with gcc attributes doesn't care.
This change is just for maximum forward compatibility for non-gcc
compilers.) This also keeps the order consistent with the previously
introduced pg_noreturn. Also update the code comment to reflect the
mentioned developments since its introduction.
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/pxr5b3z7jmkpenssra5zroxi7qzzp6eswuggokw64axmdixpnk@zbwxuq7gbbcw
We want to support a "noreturn" decoration on more compilers besides
just GCC-compatible ones, but for that we need to move the decoration
in front of the function declaration instead of either behind it or
wherever, which is the current style afforded by GCC-style attributes.
Also rename the macro to "pg_noreturn" to be similar to the C11
standard "noreturn".
pg_noreturn is now supported on all compilers that support C11 (using
_Noreturn), as well as GCC-compatible ones (using __attribute__, as
before), as well as MSVC (using __declspec). (When PostgreSQL
requires C11, the latter two variants can be dropped.)
Now, all supported compilers effectively support pg_noreturn, so the
extra code for !HAVE_PG_ATTRIBUTE_NORETURN can be dropped.
This also fixes a possible problem if third-party code includes
stdnoreturn.h, because then the current definition of
#define pg_attribute_noreturn() __attribute__((noreturn))
would cause an error.
Note that the C standard does not support a noreturn attribute on
function pointer types. So we have to drop these here. There are
only two instances at this time, so it's not a big loss. In one case,
we can make up for it by adding the pg_noreturn to a wrapper function
and adding a pg_unreachable(), in the other case, the latter was
already done before.
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/pxr5b3z7jmkpenssra5zroxi7qzzp6eswuggokw64axmdixpnk@zbwxuq7gbbcw
Add various widely useful "IWYU pragma" annotations, such as
- Common header files such as c.h, postgres.h should be "always_keep".
- System headers included in c.h, postgres.h etc. should be considered
"export".
- Some portability headers such as getopt_long.h should be
"always_keep", so they are not considered superfluous on some
platforms.
- Certain system headers included from portability headers should be
considered "export" because the purpose of the portability header is
to wrap them.
- Superfluous includes marked as "for backward compatibility" get a
formal IWYU annotation.
- Generated header included in utils/syscache.h is marked exported.
This is a very commonly used include and this avoids lots of
complaints.
Discussion: https://www.postgresql.org/message-id/flat/9395d484-eff4-47c2-b276-8e228526c8ae@eisentraut.org
Commit 962da900a added #include <stdint.h> to postgres_ext.h, which
broke c.h's header ordering rule.
The system headers on some systems would then lock down off_t's size in
private macros, before they'd had a chance to see our definition of
_FILE_OFFSET_BITS (and presumably other things). This was picked up by
perl's ABI compatibility checks on some 32 bit systems in the build
farm.
Move #include "postgres_ext.h" down below the system header section, and
make the comments clearer (thanks to Tom for the new wording).
Diagnosed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/2397643.1733347237%40sss.pgh.pa.us
Redefine our exact width types with standard C99 types and macros,
including int64_t, INT64_MAX, INT64_C(), PRId64 etc. We were already
using <stdint.h> types in a few places.
One complication is that Windows' <inttypes.h> uses format strings like
"%I64d", "%I32", "%I" for PRI*64, PRI*32, PTR*PTR, instead of mapping to
other standardized format strings like "%lld" etc as seen on other known
systems. Teach our snprintf.c to understand them.
This removes a lot of configure clutter, and should also allow 64-bit
numbers and other standard types to be used in localized messages
without casting.
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/ME3P282MB3166F9D1F71F787929C0C7E7B6312%40ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM
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
Previously we checked "for <stdbool.h> that conforms to C99" using
autoconf's AC_HEADER_STDBOOL macro. We've required C99 since PostgreSQL
12, so the test was redundant, and under C23 it was broken: autoconf
2.69's implementation doesn't understand C23's new empty header (the
macros it's looking for went away, replaced by language keywords).
Later autoconf versions fixed that, but let's just remove the
anachronistic test.
HAVE_STDBOOL_H and HAVE__BOOL will no longer be defined, but they
weren't directly tested in core or likely extensions (except in 11, see
below). PG_USE_STDBOOL (or USE_STDBOOL in 11 and 12) is still defined
when sizeof(bool) is 1, which should be true on all modern systems.
Otherwise we define our own bool type and values of size 1, which would
fail to compile under C23 as revealed by the broken test. (We'll
probably clean that dead code up in master, but here we want a minimal
back-patchable change.)
This came to our attention when GCC 15 recently started using using C23
by default and failed to compile the replacement code, as reported by
Sam James and build farm animal alligator.
Back-patch to all supported releases, and then two older versions that
also know about <stdbool.h>, per the recently-out-of-support policy[1].
12 requires C99 so it's much like the supported releases, but 11 only
assumes C89 so it now uses AC_CHECK_HEADERS instead of the overly picky
AC_HEADER_STDBOOL. (I could find no discussion of which historical
systems had <stdbool.h> but failed the conformance test; if they ever
existed, they surely aren't relevant to that policy's goals.)
[1] https://wiki.postgresql.org/wiki/Committing_checklist#Policies
Reported-by: Sam James <sam@gentoo.org>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org> (master version)
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (approach)
Discussion: https://www.postgresql.org/message-id/flat/87o72eo9iu.fsf%40gentoo.org
Like INT64_FORMAT and UINT64_FORMAT, these macros produce format
strings for 64-bit integers. However, INT64_HEX_FORMAT and
UINT64_HEX_FORMAT generate the output in hexadecimal instead of
decimal. Besides introducing these macros, this commit makes use
of them in several places. This was originally intended to be part
of commit 5d6187d2a2, but I left it out because I felt there was a
nonzero chance that back-patching these new macros into c.h could
cause problems with third-party code. We tend to be less cautious
with such changes in new major versions.
Note that UINT64_HEX_FORMAT was originally added in commit
ee1b30f128, but it was placed in test_radixtree.c, so it wasn't
widely available. This commit moves UINT64_HEX_FORMAT to c.h.
Discussion: https://postgr.es/m/ZwQvtUbPKaaRQezd%40nathan
Presently, we check for compiler support for the required
intrinsics both with and without extra compiler flags (e.g.,
-mxsave), and then depending on the results of those checks, we
pick which files to compile with which flags. This is tedious and
complicated, and it results in unsustainable coding patterns such
as separate files for each portion of code may need to be built
with different compiler flags.
This commit introduces support for __attribute__((target(...))) and
uses it for the AVX-512 code. This simplifies both the
configure-time checks and the build scripts, and it allows us to
place the functions that use the intrinsics in files that we
otherwise do not want to build with special CPU instructions. We
are careful to avoid using __attribute__((target(...))) on
compilers that do not understand it, but we still perform the
configure-time checks in case the compiler allows using the
intrinsics without it (e.g., MSVC).
A similar change could likely be made for some of the CRC-32C code,
but that is left as a future exercise.
Suggested-by: Andres Freund
Reviewed-by: Raghuveer Devulapalli, Andres Freund
Discussion: https://postgr.es/m/20240731205254.vfpap7uxwmebqeaf%40awork3.anarazel.de
Commit 15abc7788e tolerated namespace pollution from BeOS system
headers. Commit 44f902122 de-supported BeOS. Since that stuff didn't
make it into the Meson build system, synchronize by removing from
configure.
Author: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Japin Li <japinli@hotmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (the idea, not the patch)
Discussion: https://postgr.es/m/ME3P282MB3166F9D1F71F787929C0C7E7B6312%40ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM
Instead of XXX_IN_XLOCALE_H for several features XXX, let's just
include <xlocale.h> if HAVE_XLOCALE_H. The reason for the extra
complication was apparently that some old glibc systems also had an
<xlocale.h>, and you weren't supposed to include it directly, but it's
gone now (as far as I can tell it was harmless to do so anyway).
Author: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CWZBBRR6YA8D.8EHMDRGLCKCD%40neon.tech
fasthash_accum_cstring_aligned() uses a technique, found in various
strlen() implementations, to detect a string's NUL terminator by
reading a word at at time. That triggers failures when testing with
"-fsanitize=address", at least with frontend code. To enable using
this function anywhere, add a function attribute macro to disable
such testing.
Reviewed by Jeff Davis
Discussion: https://postgr.es/m/CANWCAZbwvp7oUEkbw-xP4L0_S_WNKq-J-ucP4RCNDPJnrakUPw%40mail.gmail.com
There isn't a lot of user demand for AIX support, we have a bunch of
hacks to work around AIX-specific compiler bugs and idiosyncrasies,
and no one has stepped up to the plate to properly maintain it.
Remove support for AIX to get rid of that maintenance overhead. It's
still supported for stable versions.
The acute issue that triggered this decision was that after commit
8af2565248, the AIX buildfarm members have been hitting this
assertion:
TRAP: failed Assert("(uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer)"), File: "md.c", Line: 472, PID: 2949728
Apperently the "pg_attribute_aligned(a)" attribute doesn't work on AIX
for values larger than PG_IO_ALIGN_SIZE, for a static const variable.
That could be worked around, but we decided to just drop the AIX support
instead.
Discussion: https://www.postgresql.org/message-id/20240224172345.32@rfd.leadboat.com
Reviewed-by: Andres Freund, Noah Misch, Thomas Munro
- Remove MemoryContextAllocZeroAligned(). It was supposed to be a
faster version of MemoryContextAllocZero(), but modern compilers turn
the MemSetLoop() into a call to memset() anyway, making it more or
less identical to MemoryContextAllocZero(). That was the only user of
MemSetTest, MemSetLoop, so remove those too, as well as palloc0fast().
- Convert newNode() to a static inline function. When this was
originally originally written, it was written as a macro because
testing showed that gcc didn't inline the size check as we
intended. Modern compiler versions do, and now that it just calls
palloc0() there is no size-check to inline anyway.
One nice effect is that the palloc0() takes one less argument than
MemoryContextAllocZeroAligned(), which saves a few instructions in the
callers of newNode().
Reviewed-by: Peter Eisentraut, Tom Lane, John Naylor, Thomas Munro
Discussion: https://www.postgresql.org/message-id/b51f1fa7-7e6a-4ecc-936d-90a8a1659e7c@iki.fi
These two macros wouldn't work if used in an inline function definition
in a header seen by g++, because __builtin_types_compatible_p is only
available in C. Redirect to standard C++ const_cast (which also
adds/removes volatile despite its name).
Per cpluspluscheck failure in a development branch.
Suggested-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/CA%2BhUKGK3OXFjkOyZiw-DgL2bUqk9by1uGuCnViJX786W%2BfyDSw%40mail.gmail.com
If we define ZLIB_CONST before including zlib.h, zlib augments some
interfaces with const decorations. By doing that we can keep our own
interfaces cleaner and can remove some unconstify calls.
ZLIB_CONST was introduced in zlib 1.2.5.2 (17 Dec 2011). When
compiling with older zlib releases, you might now get compiler
warnings about discarding qualifiers.
CentOS 6 has zlib 1.2.3, but in 8e278b6576, we removed support for the
OpenSSL release in CentOS 6, so it seems ok to de-support the zlib
release in CentOS 6 as well.
Reviewed-by: Tristan Partin <tristan@neon.tech>
Discussion: https://www.postgresql.org/message-id/flat/33462926-bb1e-7cc9-8d92-d86318e8ed1d%40eisentraut.org
In order to have the option to use O_DIRECT/FILE_FLAG_NO_BUFFERING in a
later commit, we need the addresses of user space buffers to be well
aligned. The exact requirements vary by OS and file system (typically
sectors and/or memory pages). The address alignment size is set to
4096, which is enough for currently known systems: it matches modern
sectors and common memory page size. There is no standard governing
O_DIRECT's requirements so we might eventually have to reconsider this
with more information from the field or future systems.
Aligning I/O buffers on memory pages is also known to improve regular
buffered I/O performance.
Three classes of I/O buffers for regular data pages are adjusted:
(1) Heap buffers are now allocated with the new palloc_aligned() or
MemoryContextAllocAligned() functions introduced by commit 439f6175.
(2) Stack buffers now use a new struct PGIOAlignedBlock to respect
PG_IO_ALIGN_SIZE, if possible with this compiler. (3) The buffer
pool is also aligned in shared memory.
WAL buffers were already aligned on XLOG_BLCKSZ. It's possible for
XLOG_BLCKSZ to be configured smaller than PG_IO_ALIGNED_SIZE and thus
for O_DIRECT WAL writes to fail to be well aligned, but that's a
pre-existing condition and will be addressed by a later commit.
BufFiles are not yet addressed (there's no current plan to use O_DIRECT
for those, but they could potentially get some incidental speedup even
in plain buffered I/O operations through better alignment).
If we can't align stack objects suitably using the compiler extensions
we know about, we disable the use of O_DIRECT by setting PG_O_DIRECT to
0. This avoids the need to consider systems that have O_DIRECT but
can't align stack objects the way we want; such systems could in theory
be supported with more work but we don't currently know of any such
machines, so it's easier to pretend there is no O_DIRECT support
instead. That's an existing and tested class of system.
Add assertions that all buffers passed into smgrread(), smgrwrite() and
smgrextend() are correctly aligned, unless PG_O_DIRECT is 0 (= stack
alignment tricks may be unavailable) or the block size has been set too
small to allow arrays of buffers to be all aligned.
Author: Thomas Munro <thomas.munro@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/CA+hUKGK1X532hYqJ_MzFWt0n1zt8trz980D79WbjwnT-yYLZpg@mail.gmail.com
New versions of perl trigger warnings within perl.h with our compiler
flags. At least -Wdeclaration-after-statement, -Wshadow=compatible-local are
known to be problematic.
To avoid these warnings, conditionally use #pragma GCC system_header before
including plperl.h.
Alternatively, we could add the include paths for problematic headers with
-isystem, but that is a larger hammer and is harder to search for.
A more granular alternative would be to use #pragma GCC diagnostic
push/ignored/pop, but gcc warns about unknown warnings being ignored, so every
to-be-ignored-temporarily compiler warning would require its own pg_config.h
symbol and #ifdef.
As the warnings are voluminous, it makes sense to backpatch this change. But
don't do so yet, we first want gather buildfarm coverage - it's e.g. possible
that some compiler claiming to be gcc compatible has issues with the pragma.
Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: Discussion: https://postgr.es/m/20221228182455.hfdwd22zztvkojy2@awork3.anarazel.de
The previous coding of VA_ARGS_NARGS() always returned 1 on Visual
Studio, because it treats __VA_ARGS__ as a single token unless you jump
through extra hoops. Newer compilers have an option to fix that. Add a
comment about that so that we can remember to clean this up in the
future when our minimum MSVC version advances.
Author: Victor Spirin <v.spirin@postgrespro.ru>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/f450fc57-a147-19d0-e50c-33571c52cc13%40postgrespro.ru
Because we added StaticAssertStmt() first before StaticAssertDecl(),
some uses as well as the instructions in c.h are now a bit backwards
from the "native" way static assertions are meant to be used in C.
This updates the guidance and moves some static assertions to better
places.
Specifically, since the addition of StaticAssertDecl(), we can put
static assertions at the file level. This moves a number of static
assertions out of function bodies, where they might have been stuck
out of necessity, to perhaps better places at the file level or in
header files.
Also, when the static assertion appears in a position where a
declaration is allowed, then using StaticAssertDecl() is more native
than StaticAssertStmt().
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/941a04e7-dd6f-c0e4-8cdf-a33b3338cbda%40enterprisedb.com
Peter Eisentraut