[gcc r17-2539] libsanitizer: Initialize local_head member [PR126307]

https://gcc.gnu.org/g:b75f76eb7fbd6314d452471d5795d24f004de5f2

commit r17-2539-gb75f76eb7fbd6314d452471d5795d24f004de5f2
Author: Jakub Jelinek <[email protected]>
Date:   Mon Jul 20 10:30:43 2026 +0200

    libsanitizer: Initialize local_head member [PR126307]
    
    The following patch cherry picks an upstream fix for this.
    
    2026-07-20  Jakub Jelinek  <[email protected]>
    
            PR sanitizer/126307
            * tsan/tsan_trace.h: Cherry-pick llvm-project revision
            cdfdb06c9155080ec97d6e4f4dd90b6e7cefb0ca.

Diff:
---
 libsanitizer/tsan/tsan_trace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libsanitizer/tsan/tsan_trace.h b/libsanitizer/tsan/tsan_trace.h
index 01bb7b34f43a..1e791ff765fe 100644
--- a/libsanitizer/tsan/tsan_trace.h
+++ b/libsanitizer/tsan/tsan_trace.h
@@ -190,7 +190,7 @@ struct Trace {
   Mutex mtx;
   IList<TraceHeader, &TraceHeader::trace_parts, TracePart> parts;
   // First node non-queued into ctx->trace_part_recycle.
-  TracePart* local_head;
+  TracePart* local_head = nullptr;
   // Final position in the last part for finished threads.
   Event* final_pos = nullptr;
   // Number of trace parts allocated on behalf of this trace specifically.