Re: Add the ability to limit the amount of memory that can be allocated to backends.

Hi,

On 2022-11-26 22:22:15 -0500, Reid Thompson wrote:
> rebased/patched to current master && current pg-stat-activity-backend-memory-allocated

This version fails to build with msvc, and builds with warnings on other
platforms.
https://cirrus-ci.com/build/5410696721072128
msvc:
[20:26:51.286] c:\cirrus\src\include\utils/backend_status.h(40): error C2059: syntax error: 'constant'

mingw cross:
[20:26:26.358] from /usr/share/mingw-w64/include/winsock2.h:23,
[20:26:26.358] from ../../src/include/port/win32_port.h:60,
[20:26:26.358] from ../../src/include/port.h:24,
[20:26:26.358] from ../../src/include/c.h:1306,
[20:26:26.358] from ../../src/include/postgres.h:47,
[20:26:26.358] from controldata_utils.c:18:
[20:26:26.358] ../../src/include/utils/backend_status.h:40:2: error: expected identifier before numeric constant
[20:26:26.358] 40 | IGNORE,
[20:26:26.358] | ^~~~~~
[20:26:26.358] In file included from ../../src/include/postgres.h:48,
[20:26:26.358] from controldata_utils.c:18:
[20:26:26.358] ../../src/include/utils/backend_status.h: In function ‘pgstat_report_allocated_bytes’:
[20:26:26.358] ../../src/include/utils/backend_status.h:365:12: error: format ‘%ld’ expects argument of type ‘long int’, but argument 3 has type ‘uint64’ {aka ‘long long unsigned int’} [-Werror=format=]
[20:26:26.358] 365 | errmsg("Backend %d deallocated %ld bytes, exceeding the %ld bytes it is currently reporting allocated. Setting reported to 0.",
[20:26:26.358] | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[20:26:26.358] 366 | MyProcPid, allocated_bytes, *my_allocated_bytes));
[20:26:26.358] | ~~~~~~~~~~~~~~~
[20:26:26.358] | |
[20:26:26.358] | uint64 {aka long long unsigned int}

Due to windows having long be 32bit, you need to use %lld. Our custom to deal
with that is to cast the argument to errmsg as long long unsigned and use
%llu.

Btw, given that the argument is uint64, it doesn't seem correct to use %ld,
that's signed. Not that it's going to matter, but ...

Greetings,

Andres Freund