Stop the linker folding main() into a skipped test - #1226
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When a test is configured out, its entry function compiles down to "return 77", the automake skip code, and the main() that forwards to it inlines to the same two instructions. Apple's ld folds the two identical bodies together and then writes LC_MAIN entryoff 0, so the binary starts executing at the Mach-O header and dies with SIGILL instead of skipping. tests/kex.test, tests/api.test and tests/auth.test all hit this under --enable-all CPPFLAGS=-DWOLFSSH_TEST_BLOCK, and kex.test hits it again under --disable-server. Probe for -Wl,-no_deduplicate and add it to AM_LDFLAGS when the linker takes it. GNU ld rejects the flag, so the check leaves Linux alone. Making the skipped body differ does not help: anything added to the entry function inlines into main() and the two fold again.
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September 3, 2026 00:18
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Fenrir Automated Review — PR #1226
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🟢 Approval recommended
The change is narrowly scoped to a conditional linker-flag probe and only applies the flag when supported, minimizing cross-platform risk while addressing the described Mach-O runtime failure.
Pull request overview
This PR updates the Autoconf configuration to prevent Apple’s ld (Mach-O) from deduplicating identical main() and “skipped test” bodies, which can otherwise result in LC_MAIN entryoff 0 and a SIGILL at runtime when a configured-out test collapses to the automake “return 77” skip path.
Changes:
- Adds a link-flag probe for
-Wl,-no_deduplicate. - Appends
-Wl,-no_deduplicatetoAM_LDFLAGSonly when the linker accepts it (leaving GNUldunaffected).
File summaries
| File | Description |
|---|---|
| configure.ac | Probes for and conditionally enables -Wl,-no_deduplicate to avoid Mach-O linker deduplication causing invalid entrypoint offsets in skipped-test binaries. |
Review details
- Files reviewed: 1/1 changed files
- Comments generated: 0
- Review effort level: Lite
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A configured-out test compiles down to "return 77" and the main()
forwarding to it inlines to the same body, so Apple's ld folds the two
and writes LC_MAIN entryoff 0: the binary starts executing at the Mach-O
header and dies with SIGILL instead of skipping.
takes it. GNU ld rejects the flag, so Linux is left alone.
--enable-all CPPFLAGS=-DWOLFSSH_TEST_BLOCK, and kex.test again under
--disable-server.