Copilot commented on code in PR #13610:
URL: https://github.com/apache/trafficserver/pull/13610#discussion_r3918045969
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CMakeLists.txt:
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@@ -449,6 +450,43 @@ elseif(ENABLE_TSAN)
add_link_options(-g -fsanitize=thread)
endif()
+# UndefinedBehaviorSanitizer. Deliberately not part of the either/or chain
above:
+# UBSan instruments arithmetic, shifts, and type loads rather than replacing
the
+# allocator or the thread runtime, so it composes with either of them as well
as
+# standing on its own: asan gives -fsanitize=address,undefined and tsan gives
+# -fsanitize=thread,undefined. Only the asan pairing has a preset, since that
is
+# the combination developers ask for, but the option itself does not restrict
it.
+#
+# vptr is excluded. It needs a matching type_info at every polymorphic access,
and
+# a plugin loaded with dlopen does not reliably share type identity with the
main
+# image, so the check reports the plugin boundary rather than a real bug.
+#
+# Findings recover, so a single run reports every distinct site instead of
stopping
+# at the first. That is the default for most checks, but which checks recover
by
+# default varies between compilers, so ask for it explicitly rather than
inherit it.
+# A few checks cannot recover by construction (unreachable, return) and still
abort.
+# Set UBSAN_OPTIONS=halt_on_error=1 at runtime to stop on the first finding,
which
+# is what a gating job would want.
+if(ENABLE_UBSAN)
+ # This can fail two ways: the toolchain does not know -fsanitize=undefined
at all,
+ # or it knows the flag but cannot link the runtime library, which some
distributions
+ # package separately from the compiler. Without the check the second case
surfaces as
+ # a bare "cannot find libubsan.so" from the linker after compiling hundreds
of
+ # objects, so establish it here and let the message cover both.
+ include(CheckLinkerFlag)
+ check_linker_flag(CXX -fsanitize=undefined HAS_UBSAN_SUPPORT)
+ if(NOT HAS_UBSAN_SUPPORT)
+ message(
+ FATAL_ERROR
+ "ENABLE_UBSAN was requested, but this toolchain cannot link
-fsanitize=undefined. Either the compiler does not support the flag, or it does
and the sanitizer runtime is missing. If the compiler is GCC, that runtime is
the libubsan package."
Review Comment:
The fatal error message hard-codes a specific distro package name ("the
libubsan package"). On some platforms (e.g., Debian/Ubuntu), the GCC UBSan
runtime is packaged under different names (commonly libubsan1), so this
guidance can be misleading even though the underlying diagnosis is correct.
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