Remove configure's checks for HAVE_POSIX_SIGNALS, HAVE_SIGPROCMASK, and
HAVE_SIGSETJMP. These APIs are required by the Single Unix Spec v2
(POSIX 1997), which we generally consider to define our minimum required
set of Unix APIs. Moreover, no buildfarm member has reported not having
them since 2012 or before, which means that even if the code is still live
somewhere, it's untested --- and we've made plenty of signal-handling
changes of late. So just take these APIs as given and save the cycles for
configure probes for them.
However, we can't remove as much C code as I'd hoped, because the Windows
port evidently still uses the non-POSIX code paths for signal masking.
Since we're largely emulating these BSD-style APIs for Windows anyway, it
might be a good thing to switch over to POSIX-like notation and thereby
remove a few more #ifdefs. But I'm not in a position to code or test that.
In the meantime, we can at least make things a bit more transparent by
testing for WIN32 explicitly in these places.
C89 requires <signal.h> to define sig_atomic_t, and there is no evidence
in the buildfarm that any supported platforms don't comply. Remove the
configure test to stop wasting build cycles on a purely historical issue.
(Once upon a time, we cared about supporting C89-compliant compilers on
machines with pre-C89 system headers, but that use-case has been dead for
quite a few years.)
I have some other fixes planned in this area, but let's start with this
to see if the buildfarm produces any surprising results.
In de6fd1c8 I moved the the work around from 53f73879 into the aix
template. The previous location was removed in the former commit, and I
thought that it would be nice to emit a warning when running configure.
That didn't turn out to work because at the point the template is
included we don't know whether we're compiling a 32/64 bit binary and
it's possible to install compilers for both on a 64 bit kernel/OS.
So go back to a less ambitious approach and define
PG_FORCE_DISABLE_INLINE in port/aix.h, without emitting a warning. We
could try a more fancy approach, but it doesn't seem worth it.
This requires moving the check for PG_FORCE_DISABLE_INLINE in c.h to
after including the system headers included from therein which isn't
perfect, as it seems slightly more robust to include all system headers
in a similar environment. Oh well.
Discussion: 20150807132000.GC13310@awork2.anarazel.de
So far we have worked around the fact that some very old compilers do
not support 'inline' functions by only using inline functions
conditionally (or not at all). Since such compilers are very rare by
now, we have decided to rely on inline functions from 9.6 onwards.
To avoid breaking these old compilers inline is defined away when not
supported. That'll cause "function x defined but not used" type of
warnings, but since nobody develops on such compilers anymore that's
ok.
This change in policy will allow us to more easily employ inline
functions.
I chose to remove code previously conditional on PG_USE_INLINE as it
seemed confusing to have code dependent on a define that's always
defined.
Blacklisting of compilers, like in c53f73879f, now has to be done
differently. A platform template can define PG_FORCE_DISABLE_INLINE to
force inline to be defined empty.
Discussion: 20150701161447.GB30708@awork2.anarazel.de
In 83ff1618 we defined integer limits iff they're not provided by the
system. That turns out not to be the greatest idea because there's
different ways some datatypes can be represented. E.g. on OSX PG's 64bit
datatype will be a 'long int', but OSX unconditionally uses 'long
long'. That disparity then can lead to warnings, e.g. around printf
formats.
One way to fix that would be to back int64 using stdint.h's
int64_t. While a good idea it's not that easy to implement. We would
e.g. need to include stdint.h in our external headers, which we don't
today. Also computing the correct int64 printf formats in that case is
nontrivial.
Instead simply prefix the integer limits with PG_ and define them
unconditionally. I've adjusted all the references to them in code, but
not the ones in comments; the latter seems unnecessary to me.
Discussion: 20150331141423.GK4878@alap3.anarazel.de
This improves on commit bbfd7edae5 by
making two simple changes:
* pg_attribute_noreturn now takes parentheses, ie pg_attribute_noreturn().
Likewise pg_attribute_unused(), pg_attribute_packed(). This reduces
pgindent's tendency to misformat declarations involving them.
* attributes are now always attached to function declarations, not
definitions. Previously some places were taking creative shortcuts,
which were not merely candidates for bad misformatting by pgindent
but often were outright wrong anyway. (It does little good to put a
noreturn annotation where callers can't see it.) In any case, if
we would like to believe that these macros can be used with non-gcc
compilers, we should avoid gratuitous variance in usage patterns.
I also went through and manually improved the formatting of a lot of
declarations, and got rid of excessively repetitive (and now obsolete
anyway) comments informing the reader what pg_attribute_printf is for.
Several submitted and even committed patches have run into the problem
that C89, our baseline, does not provide minimum/maximum values for
various integer datatypes. C99's stdint.h does, but we can't rely on
it.
Several parts of the code defined limits locally, so instead centralize
the definitions to c.h.
This patch also changes the more obvious usages of literal limit values;
there's more places that could be changed, but it's less clear whether
it's beneficial to change those.
Author: Andrew Gierth
Discussion: 87619tc5wc.fsf@news-spur.riddles.org.uk
We will, for the foreseeable future, not expose 128 bit datatypes to
SQL. But being able to use 128bit math will allow us, in a later patch,
to use 128bit accumulators for some aggregates; leading to noticeable
speedups over using numeric.
So far we only detect a gcc/clang extension that supports 128bit math,
but no 128bit literals, and no *printf support. We might want to expand
this in the future to further compilers; if there are any that that
provide similar support.
Discussion: 544BB5F1.50709@proxel.se
Author: Andreas Karlsson, with significant editorializing by me
Reviewed-By: Peter Geoghegan, Oskari Saarenmaa
Until now __attribute__() was defined to be empty for all compilers but
gcc. That's problematic because it prevents using it in other compilers;
which is necessary e.g. for atomics portability. It's also just
generally dubious to do so in a header as widely included as c.h.
Instead add pg_attribute_format_arg, pg_attribute_printf,
pg_attribute_noreturn macros which are implemented in the compilers that
understand them. Also add pg_attribute_noreturn and pg_attribute_packed,
but don't provide fallbacks, since they can affect functionality.
This means that external code that, possibly unwittingly, relied on
__attribute__ defined to be empty on !gcc compilers may now run into
warnings or errors on those compilers. But there shouldn't be many
occurances of that and it's hard to work around...
Discussion: 54B58BA3.8040302@ohmu.fi
Author: Oskari Saarenmaa, with some minor changes by me.
Replace some bogus "x[1]" declarations with "x[FLEXIBLE_ARRAY_MEMBER]".
Aside from being more self-documenting, this should help prevent bogus
warnings from static code analyzers and perhaps compiler misoptimizations.
This patch is just a down payment on eliminating the whole problem, but
it gets rid of a lot of easy-to-fix cases.
Note that the main problem with doing this is that one must no longer rely
on computing sizeof(the containing struct), since the result would be
compiler-dependent. Instead use offsetof(struct, lastfield). Autoconf
also warns against spelling that offsetof(struct, lastfield[0]).
Michael Paquier, review and additional fixes by me.
Benchmarks has shown that aligning the buffer descriptor array to
cache lines is important for scalability; especially on bigger,
multi-socket, machines.
Currently the array sometimes already happens to be aligned by
happenstance, depending how large previous shared memory allocations
were. That can lead to wildly varying performance results after minor
configuration changes.
In addition to aligning the start of descriptor array, also force the
size of individual descriptors to be of a common cache line size (64
bytes). That happens to already be the case on 64bit platforms, but
this way we can change the struct BufferDesc more easily.
As the alignment primarily matters in highly concurrent workloads
which probably all are 64bit these days, and the space wastage of
element alignment would be a bit more noticeable on 32bit systems, we
don't force the stride to be cacheline sized on 32bit platforms for
now. If somebody does actual performance testing, we can reevaluate
that decision by changing the definition of BUFFERDESC_PADDED_SIZE.
Discussion: 20140202151319.GD32123@awork2.anarazel.de
Per discussion with Bruce Momjan, Tom Lane, Robert Haas, and Peter
Geoghegan.
Several upcoming performance/scalability improvements require atomic
operations. This new API avoids the need to splatter compiler and
architecture dependent code over all the locations employing atomic
ops.
For several of the potential usages it'd be problematic to maintain
both, a atomics using implementation and one using spinlocks or
similar. In all likelihood one of the implementations would not get
tested regularly under concurrency. To avoid that scenario the new API
provides a automatic fallback of atomic operations to spinlocks. All
properties of atomic operations are maintained. This fallback -
obviously - isn't as fast as just using atomic ops, but it's not bad
either. For one of the future users the atomics ontop spinlocks
implementation was actually slightly faster than the old purely
spinlock using implementation. That's important because it reduces the
fear of regressing older platforms when improving the scalability for
new ones.
The API, loosely modeled after the C11 atomics support, currently
provides 'atomic flags' and 32 bit unsigned integers. If the platform
efficiently supports atomic 64 bit unsigned integers those are also
provided.
To implement atomics support for a platform/architecture/compiler for
a type of atomics 32bit compare and exchange needs to be
implemented. If available and more efficient native support for flags,
32 bit atomic addition, and corresponding 64 bit operations may also
be provided. Additional useful atomic operations are implemented
generically ontop of these.
The implementation for various versions of gcc, msvc and sun studio have
been tested. Additional existing stub implementations for
* Intel icc
* HUPX acc
* IBM xlc
are included but have never been tested. These will likely require
fixes based on buildfarm and user feedback.
As atomic operations also require barriers for some operations the
existing barrier support has been moved into the atomics code.
Author: Andres Freund with contributions from Oskari Saarenmaa
Reviewed-By: Amit Kapila, Robert Haas, Heikki Linnakangas and Álvaro Herrera
Discussion: CA+TgmoYBW+ux5-8Ja=Mcyuy8=VXAnVRHp3Kess6Pn3DMXAPAEA@mail.gmail.com,
20131015123303.GH5300@awork2.anarazel.de,
20131028205522.GI20248@awork2.anarazel.de
We have had INT64_FORMAT and UINT64_FORMAT for a long time, but that's not
good enough if you want something more exotic, like "%20lld".
Abhijit Menon-Sen, per Andres Freund's suggestion.
The existance of the assert_enabled variable (backing the
debug_assertions GUC) reduced the amount of knowledge some static code
checkers (like coverity and various compilers) could infer from the
existance of the assertion. That could have been solved by optionally
removing the assertion_enabled variable from the Assert() et al macros
at compile time when some special macro is defined, but the resulting
complication doesn't seem to be worth the gain from having
debug_assertions. Recompiling is fast enough.
The debug_assertions GUC is still available, but readonly, as it's
useful when diagnosing problems. The commandline/client startup option
-A, which previously also allowed to enable/disable assertions, has
been removed as it doesn't serve a purpose anymore.
While at it, reduce code duplication in bufmgr.c and localbuf.c
assertions checking for spurious buffer pins. That code had to be
reindented anyway to cope with the assert_enabled removal.
_WIN32 is set by the compiler, whereas our code uses WIN32 that is
normally set through our build system. To make it possible to build
extensions out of tree we cannot rely on that, so set the WIN32
symbol explicitly whenever the compiler has set _WIN32.
Not setting this symbol causes double inclusion of pg_config_os.h,
and possibly other errors as well.
Craig Ringer
Remove the use of the following macros, which are obsolescent according
to the Autoconf documentation:
- AC_C_CONST
- AC_C_STRINGIZE
- AC_C_VOLATILE
- AC_FUNC_MEMCMP
This avoids an assumption about the signed number representation. It is
anticipated to have no functional changes on supported configurations;
many two's complement assumptions remain elsewhere.
Per a suggestion from Andres Freund.
The TYPEALIGN macro, and the related ones like MAXALIGN, don't work with
values larger than intptr_t, because TYPEALIGN casts the argument to
intptr_t to do the arithmetic. That's not a problem when dealing with
pointers or lengths or offsets related to pointers, but the XLogInsert
scaling patch added a call to MAXALIGN with an XLogRecPtr argument.
To fix, add wider variants of the macros, called TYPEALIGN64 and MAXALIGN64,
which are just like the existing variants but work with uint64 instead of
intptr_t.
Report and patch by David Rowley, analysis by Andres Freund.
In some cases, the use of these macros may be preferable to Assert()
or AssertMacro(), since this way the caller can set the trap message.
Andres Freund and Robert Haas
It needs to be defined in the backend even when assertions are not
enabled. It's cleaner to put it back, than create a separate #ifdef
section in c.h.
Per trouble report from Jeff Janes
This way, they can be used by frontend and backend code. We already
supported that, but doing it this way allows us to mix true frontend
files with backend files compiled in frontend environment.
Author: Andres Freund
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
The former name was too likely to conflict with symbols from external
headers; and, as seen in recent buildfarm failures in member spoonbill,
it has now happened at least in plpython.
We already had those, but they forced modules to spell out the function
bodies twice. Eliminate some duplicates we had already grown.
Extracted from a somewhat larger patch from Andres Freund.
Get rid of the fundamentally indefensible assumption that "long long int"
exists and is exactly 64 bits wide on every platform Postgres runs on.
Instead let the configure script select the type to use for "pg_int64".
This is a bit of a pain in the rear since we do not want to pollute client
namespace with all the random symbols that pg_config.h defines; instead
we have to create a separate generated header file, "pg_config_ext.h".
But now that the infrastructure is there, we might have the ability to
add some other stuff that's long been wanting in this area.
On reflection (especially after noticing how many buildfarm critters have
__builtin_types_compatible_p but not _Static_assert), it seems like we
ought to try a bit harder to make these macros do something everywhere.
The initial cut at it would have been no help to code that is compiled only
on platforms without _Static_assert, for instance; and in any case not all
our contributors do their initial coding on the latest gcc version.
Some googling about static assertions turns up quite a bit of prior art
for making it work in compilers that lack _Static_assert. The method
that seems closest to our needs involves defining a struct with a bit-field
that has negative width if the assertion condition fails. There seems no
reliable way to get the error message string to be output, but throwing a
compile error with a confusing message is better than missing the problem
altogether.
In the same spirit, if we don't have __builtin_types_compatible_p we can at
least insist that the variable have the same width as the type. This won't
catch errors such as "wrong pointer type", but it's far better than
nothing.
In addition to changing the macro definitions, adjust a
compile-time-constant Assert in contrib/hstore to use StaticAssertStmt,
so we can get some buildfarm coverage on whether that macro behaves sanely
or not. There's surely more places that could be converted, but this is
the first one I came across.
Currently, the macros only work with fairly recent gcc versions, but there
is room to expand them to other compilers that have comparable features.
Heavily revised and autoconfiscated version of a patch by Andres Freund.
The latter was already the dominant use, and it's preferable because
in C the convention is that intXX means XX bits. Therefore, allowing
mixed use of int2, int4, int8, int16, int32 is obviously confusing.
Remove the typedefs for int2 and int4 for now. They don't seem to be
widely used outside of the PostgreSQL source tree, and the few uses
can probably be cleaned up by the time this ships.
For those variables only used when asserts are enabled, use a new
macro PG_USED_FOR_ASSERTS_ONLY, which expands to
__attribute__((unused)) when asserts are not enabled.
Original patch by Lars Kanis, reviewed by Nishiyama Tomoaki and tweaked some by me.
This compiler, or at least the latest version of it, is currently broken, and
only passes the regression tests if built with -O0.
The style is set to "printf" for backwards compatibility everywhere except
on Windows, where it is set to "gnu_printf", which eliminates hundreds of
false error messages from modern versions of gcc arising from %m and %ll{d,u}
formats.
This can be used to build 64 bit Windows binaries, not only on 64 bit
Windows but on supported cross-compiling hosts including 32 bit Windows,
Cygwin, Darwin and Linux.
Tom Lane