https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/181138
Backport 0991d7b8fd01546aaf537a6238227100570f8236 Requested by: @mstorsjo >From 74d49502c5105bc8da7b90a430d94b1e13a958d6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <[email protected]> Date: Thu, 12 Feb 2026 00:31:09 +0200 Subject: [PATCH] [libunwind] Fix building with EXCEPTION_DISPOSITION as enum (#180513) On Windows, libunwind is normally only built in mingw mode; it's not relevant for MSVC targets. (Attempting to build it is entirely blocked in CMake, see [1]). In mingw headers, the type EXCEPTION_DISPOSITION is defined as an int while it is an enum in the MSVC vcruntime headers. However, in addition to the canonical enum members, we also use a value which has no assigned enum member. In older mingw-w64 headers, there was a define for this value, 4, with the name ExceptionExecuteHandler, but that was removed in [2]. The libunwind code reference this value just by the literal value 4, with a comment referencing it as ExceptionExecuteHandler. This extra enum value isn't passed to the outside Microsoft runtime, but is only used to pass values from one part of libunwind to another; this handling is necessary for the forced_unwind{1-3}.pass.cpp tests to succeed. If the mingw-w64 headers would define EXCEPTION_DISPOSITION as an enum, just like the MSVC vcruntime headers, then we'd run into build errors and warnings like this: llvm-project/libunwind/src/Unwind-seh.cpp:166:14: error: cannot initialize return object of type 'EXCEPTION_DISPOSITION' (aka 'enum _EXCEPTION_DISPOSITION') with an rvalue of type 'int' 166 | return 4 /* ExceptionExecuteHandler in mingw */; | ^ llvm-project/libunwind/src/Unwind-seh.cpp:185:14: error: cannot initialize return object of type 'EXCEPTION_DISPOSITION' (aka 'enum _EXCEPTION_DISPOSITION') with an rvalue of type 'int' 185 | return 4 /* ExceptionExecuteHandler in mingw */; | ^ llvm-project/libunwind/src/Unwind-seh.cpp:272:8: warning: case value not in enumerated type 'EXCEPTION_DISPOSITION' (aka 'enum _EXCEPTION_DISPOSITION') [-Wswitch] 272 | case 4 /*ExceptionExecuteHandler*/: | ^ Fix these cases by adding explicit casts between EXCEPTION_DISPOSITION and int. A (partial) similar change was proposed in [3], but the author never followed up on the discussion, and the PR was later closed. [1] b0b546d44777eb1fa25995384876bd14a006a929 [2] https://github.com/mingw-w64/mingw-w64/commit/2de6703961c0d519046b841f7b392a040e1e5b55 [3] https://github.com/llvm/llvm-project/pull/159293 (cherry picked from commit 0991d7b8fd01546aaf537a6238227100570f8236) --- libunwind/src/Unwind-seh.cpp | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/libunwind/src/Unwind-seh.cpp b/libunwind/src/Unwind-seh.cpp index 110c5987c3f1a..0b1930b44d1c6 100644 --- a/libunwind/src/Unwind-seh.cpp +++ b/libunwind/src/Unwind-seh.cpp @@ -163,7 +163,7 @@ _GCC_specific_handler(PEXCEPTION_RECORD ms_exc, PVOID frame, PCONTEXT ms_ctx, // If we were called by __libunwind_seh_personality(), indicate that // a handler was found; otherwise, initiate phase 2 by unwinding. if (ours && ms_exc->NumberParameters > 1) - return 4 /* ExceptionExecuteHandler in mingw */; + return static_cast<EXCEPTION_DISPOSITION>(4); // This should never happen in phase 2. if (IS_UNWINDING(ms_exc->ExceptionFlags)) _LIBUNWIND_ABORT("Personality indicated exception handler in phase 2!"); @@ -182,7 +182,7 @@ _GCC_specific_handler(PEXCEPTION_RECORD ms_exc, PVOID frame, PCONTEXT ms_ctx, // a handler was found; otherwise, it's time to initiate a collided // unwind to the target. if (ours && !IS_UNWINDING(ms_exc->ExceptionFlags) && ms_exc->NumberParameters > 1) - return 4 /* ExceptionExecuteHandler in mingw */; + return static_cast<EXCEPTION_DISPOSITION>(4); // This should never happen in phase 1. if (!IS_UNWINDING(ms_exc->ExceptionFlags)) _LIBUNWIND_ABORT("Personality installed context during phase 1!"); @@ -259,13 +259,12 @@ __libunwind_seh_personality(int version, _Unwind_Action state, (void *)disp_ctx->LanguageHandler, (void *)&ms_exc, (void *)disp_ctx->EstablisherFrame, (void *)disp_ctx->ContextRecord, (void *)disp_ctx); - EXCEPTION_DISPOSITION ms_act = disp_ctx->LanguageHandler(&ms_exc, - (PVOID)disp_ctx->EstablisherFrame, - disp_ctx->ContextRecord, - disp_ctx); + int ms_act = static_cast<int>( + disp_ctx->LanguageHandler(&ms_exc, (PVOID)disp_ctx->EstablisherFrame, + disp_ctx->ContextRecord, disp_ctx)); _LIBUNWIND_TRACE_UNWINDING("__libunwind_seh_personality() LanguageHandler " "returned %d", - (int)ms_act); + ms_act); switch (ms_act) { case ExceptionContinueExecution: return _URC_END_OF_STACK; case ExceptionContinueSearch: return _URC_CONTINUE_UNWIND; _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
