Add check for SYS_gettid support

[apeskov]

To improve compatibility with old glibc version which lack syscall(SYS_gettid) will use pthread_self() as a fallback.

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[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Alexander Peskov (apeskov)

Changes

To improve compatibility with old glibc version which lack syscall(SYS_gettid) will use pthread_self() as a fallback.

---

Full diff: https://github.com/llvm/llvm-project/pull/119742.diff

1 Files Affected:

• (modified) llvm/lib/Support/Unix/Threading.inc (+1-1)

diff --git a/llvm/lib/Support/Unix/Threading.inc b/llvm/lib/Support/Unix/Threading.inc
index c7b4c7af3b9f33..368e3cf1c5bd8f 100644
--- a/llvm/lib/Support/Unix/Threading.inc
+++ b/llvm/lib/Support/Unix/Threading.inc
@@ -140,7 +140,7 @@ uint64_t llvm::get_threadid() {
   return uint64_t(getthrid());
 #elif defined(__ANDROID__)
   return uint64_t(gettid());
-#elif defined(__linux__)
+#elif defined(__linux__) && defined(SYS_gettid)
   return uint64_t(syscall(SYS_gettid));
 #else
   return uint64_t(pthread_self());

[apeskov]

@brad0 @devnexen
Could you please take a look on this change?

[brad0]

It would be better to change SYS_gettid to __NR_gettid.

I posted a PR here.

#120007

[apeskov]

Ok, __NR_gettid will suite me as well. Thanks!

Your PR already passed some checks so I will not update this one.