gettid() is undeclared (Linux)

[davidebeatrici]

Describe the bug

A test fails to compile due to the gettid() function being undeclared.

Reproduction Steps

v vlib/v/tests/trace_calls_test.v

Expected Behavior

The test to succeed.

Current Behavior

The test fails to compile:

 FAIL  [2077/2214] C:   447.2 ms, R:   750.467 ms vlib/v/tests/trace_calls_test.v
> trace_fns_only_println compilation output:
================== C compilation error (from cc): ==============
cc: /tmp/v_1001/tsession_7f5da030e740_01JGMW261EACT7W3A17Q67E947/single_println.01JGMW7YBVE9N13HGQ7BHP4SR6.tmp.c:14022:10: error: call to undeclared function 'gettid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
cc:  14022 |                         tid = gettid();
cc:        |                               ^
cc: 1 error generated.
================================================================

Possible Solution

https://stackoverflow.com/questions/61979901/gcc-warns-about-gettid-syscall-wrapper-with-glibc-2-30-8

Additional Information/Context

No response

V version

0.4.9

Environment details (OS name and version, etc.)

V full version: V 0.4.9 3953445
OS: linux, "OpenMandriva Lx 24.90" (VM)
Processor: 8 cpus, 64bit, little endian, AMD Ryzen 9 5900X 12-Core Processor

getwd: /tmp/v-0.4.9
vexe: /tmp/v-0.4.9/v
vexe mtime: 2025-01-03 01:18:56

vroot: OK, value: /tmp/v-0.4.9
VMODULES: OK, value: /home/user/.vmodules
VTMP: OK, value: /tmp/v_1001

Git version: git version 2.47.1
Git vroot status: 08d5c282-dirty
.git/config present: false

CC version: OpenMandriva 19.1.6-1 clang version 19.1.6 (/builddir/build/BUILD/llvm-19.1.6-build/llvm-project-llvmorg-19.1.6/clang 1cc1c8b2641ccba94c7b90b5e4c4e500729f7556)
emcc version: N/A
thirdparty/tcc: N/A

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_{Huly®: V_0.6-21782}

[JalonSolov]

Appears to be just your version of Linux.

On Manjaro, I get this:

$ v vlib/v/tests/trace_calls_test.v
> `-trace-calls -trace-fns PATTERNS` works
------------------------------
> 64bit trace output of vlib/v/tests/testdata/trace_calls/single_println.vv matches line pattern: *hi*
> skipping -m32 compilation since either 32bit headers are not installed, or you do not have gcc installed
------------------------------
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * C.main*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * _vinit*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * main main.main/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * main main.foo/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * main main.bar/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * main main.baz/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * main main.Boo.call_1/1*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * builtin eprintln/1*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/simple.vv matches line pattern: *> trace * _vcleanup*
> skipping -m32 compilation since either 32bit headers are not installed, or you do not have gcc installed
------------------------------
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * C.main*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * _vinit*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * builtin arguments/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * main main.main/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * main main.f1/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * main main.f2/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * main main.f3/0*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace * os os.join_path/2*
> 64bit trace output of vlib/v/tests/testdata/trace_calls/with_modules.vv matches line pattern: *> trace *_vcleanup*
> skipping -m32 compilation since either 32bit headers are not installed, or you do not have gcc installed
------------------------------
$

[davidebeatrici]

Are you using glibc or musl?

[JalonSolov]

glibc

[felipensp]

Currently we already do:

#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 30
#include <sys/syscall.h>
#define gettid() syscall(SYS_gettid)
#endif

This was added to fix such error on Debian 10.

[davidebeatrici]

For reference, OpenMandriva currently has glibc 2.40.

v/vlib/v/gen/c/cgen.v

Lines 952 to 957 in c50d4ee

	if g.pref.os == .linux {
	g.cheaders.writeln('#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 30')
	g.cheaders.writeln('#include <sys/syscall.h>')
	g.cheaders.writeln('#define gettid() syscall(SYS_gettid)')
	g.cheaders.writeln('#endif')
	}

@felipensp I believe we should either:

1. Do that for all glibc versions.
2. Do this for glibc >= 2.30:

#define _GNU_SOURCE
#include <unistd.h>