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gh-144194: Fix mmap failure check in perf_jit_trampoline.c #143713

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gh-144194: Fix mmap failure check in perf_jit_trampoline.c #143713

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-01-23-20-20-42.gh-issue-144194.IbXfxd.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix mmap failure check in perf jitdump initialization. The code incorrectly
checked for NULL instead of MAP_FAILED, causing failures to go undetected.
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@StanFromIreland StanFromIreland Jan 23, 2026

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Can the news entry focus on what was fixed, not how (that's what we have diffs for). They are for end-users, not people familiar with internals.

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@stratakis stratakis Jan 24, 2026

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What would you suggest? This is a fix for the internals after all that I noticed myself in the code, while working on another issue. And fixes for such types of issues have been many times in NEWS entries before, other times the NEWS entry is skipped, which is what I was going for in this case.

3 changes: 2 additions & 1 deletion Python/perf_jit_trampoline.c
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Expand Up @@ -1083,7 +1083,8 @@ static void* perf_map_jit_init(void) {
0 // Offset 0 (first page)
);

if (perf_jit_map_state.mapped_buffer == NULL) {
if (perf_jit_map_state.mapped_buffer == MAP_FAILED) {
perf_jit_map_state.mapped_buffer = NULL;
close(fd);
return NULL; // Memory mapping failed
}
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