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In Subversion r268025 (Git commit3f21b8e3f7) "Add dg-require-effective-target exceptions", effective-target 'exceptions' was added, which "says that AMD GCN does not support [exception handling]". In Subversion r279246 (Git commita9046e9853) "MSP430: Add -fno-exceptions multilib", effective-target 'exceptions_enabled' was added "to check if the testing configuration supports exceptions". Testing "if exceptions are unsupported or disabled (e.g. by passing -fno-exceptions)" works as expected if exception handling is disabled at the front-end level ('-fno-exceptions'; the "exceptions are [...] disabled" case): exceptions_enabled2066068.cc: In function ‘void foo()’: exceptions_enabled2066068.cc:3:27: error: exception handling disabled, use ‘-fexceptions’ to enable However, effective-target 'exceptions_enabled' additionally assumes that "If exceptions aren't supported [by the target], then they're not enabled". This is not correct: it's not unlikely that, in presence of explicit/implicit '-fexceptions', exception handling code gets fully optimized away by the compiler, and therefore effective-target 'exceptions_enabled' test cases may PASS even for targets that don't support effective-target 'exceptions'; these two effective-targets are orthogonal concepts. (For completeness: code with trivial instances of C++ exception handling may translate into simple '__cxa_allocate_exception', '__cxa_throw' function calls without requiring any back end-level "exceptions magic", and then trigger unresolved symbols at link time, if these functions are not available.) This change only affects GCN, as that one currently is the only target declared as not supporting effective-target 'exceptions'. gcc/ * doc/sourcebuild.texi (Effective-Target Keywords): Clarify that effective-target 'exceptions' and 'exceptions_enabled' are orthogonal. gcc/testsuite/ * lib/gcc-dg.exp (gcc-dg-prune): Clarify effective-target 'exceptions_enabled'. * lib/target-supports.exp (check_effective_target_exceptions_enabled): Don't consider effective-target 'exceptions'. libstdc++-v3/ * testsuite/lib/prune.exp (libstdc++-dg-prune): Clarify effective-target 'exceptions_enabled'.
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