[libc++] Add checks for misused hardening macros #150669
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Libc++ hardening went through several iterations, sometimes within a single release. However, some folks in the wide have picked up these macros that were either public at some point or that were used temporarily on `main`, and unfortunately those are now ignored. This can lead to some users thinking they enable hardening when in reality they don't, which is a pretty big deal. This patch simply checks various old hardening-related macros and ensures that they are not set, which will catch such misuse.
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@llvm/pr-subscribers-libcxx Author: Louis Dionne (ldionne) ChangesLibc++ hardening went through several iterations, sometimes within a single release. However, some folks in the wide have picked up these macros that were either public at some point or that were used temporarily on This can lead to some users thinking they enable hardening when in reality they don't, which is a pretty big deal. This patch simply checks various old hardening-related macros and ensures that they are not set, which will catch such misuse. Full diff: https://github.com/llvm/llvm-project/pull/150669.diff 1 Files Affected:
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 3fe377aac4816..ef7aa0a69ba92 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -40,9 +40,21 @@
// HARDENING {
-// TODO: Remove in LLVM 21. We're making this an error to catch folks who might not have migrated.
-# ifdef _LIBCPP_ENABLE_ASSERTIONS
-# error "_LIBCPP_ENABLE_ASSERTIONS has been removed, please use _LIBCPP_HARDENING_MODE instead"
+// TODO: Remove in LLVM 23. We're making these an error to catch folks who might not have migrated.
+// Since hardening went through several changes (many of which impacted user-facing macros),
+// we're keeping these checks around for a bit longer than usual. Failure to properly configure
+// hardening results in checks being dropped silently, which is a pretty big deal.
+# if defined(_LIBCPP_ENABLE_ASSERTIONS)
+# error "_LIBCPP_ENABLE_ASSERTIONS has been removed, please use _LIBCPP_HARDENING_MODE=<mode> instead (see docs)"
+# endif
+# if defined(_LIBCPP_ENABLE_HARDENED_MODE)
+# error "_LIBCPP_ENABLE_HARDENED_MODE has been removed, please use _LIBCPP_HARDENING_MODE=<mode> instead (see docs)"
+# endif
+# if defined(_LIBCPP_ENABLE_SAFE_MODE)
+# error "_LIBCPP_ENABLE_SAFE_MODE has been removed, please use _LIBCPP_HARDENING_MODE=<mode> instead (see docs)"
+# endif
+# if defined(_LIBCPP_ENABLE_DEBUG_MODE)
+# error "_LIBCPP_ENABLE_DEBUG_MODE has been removed, please use _LIBCPP_HARDENING_MODE=<mode> instead (see docs)"
# endif
// The library provides the macro `_LIBCPP_HARDENING_MODE` which can be set to one of the following values:
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philnik777
reviewed
Jul 26, 2025
Co-authored-by: Nikolas Klauser <[email protected]>
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@philnik777 Are you OK with this? This originated when a user reached out to me and we realized that they had hardening turned off because they had been an early adopter of the feature. So I think there's value in catching that explicitly. |
philnik777
approved these changes
Jul 30, 2025
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/cherry-pick 955ece4 |
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/pull-request #151582 |
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Libc++ hardening went through several iterations, sometimes within a single release. However, some folks in the wild have picked up these macros that were either public at some point or that were used temporarily on
main, and unfortunately those are now ignored.This can lead to some users thinking they enable hardening when in reality they don't, which is a pretty big deal. This patch simply checks various old hardening-related macros and ensures that they are not set, which will catch such misuse.