[libcxxabi] declare __gnu_unwind_frame when not using libunwind

[planetmarshall]

#116261 removed the declaration of __gnu_unwind_frame and moved it to libunwind, however libunwind is not a required component for libcxxabi. Specifically, this does not compile for ARMv7 targets when libunwind is configured as part of llvm-libgcc where we must have LIBCXXABI_USE_LLVM_UNWINDER=OFF

This PR restores the declaration of __gnu_unwind_frame for ARMv7 targets when _LIBUNWIND_VERSION is not defined.

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[llvmbot]

@llvm/pr-subscribers-libcxxabi

Author: Andrew Marshall (planetmarshall)

Changes

#116261 removed the declaration of __gnu_unwind_frame and moved it to libunwind, however libunwind is not a required component for libcxxabi. Specifically, this does not compile when libunwind is configured as part of llvm-libgcc where we must have LIBCXXABI_USE_LLVM_UNWINDER=OFF

This PR restores the declaration of __gnu_unwind_frame when _LIBUNWIND_VERSION is not defined.

---

Full diff: https://github.com/llvm/llvm-project/pull/189280.diff

1 Files Affected:

• (modified) libcxxabi/src/cxa_personality.cpp (+5)

diff --git a/libcxxabi/src/cxa_personality.cpp b/libcxxabi/src/cxa_personality.cpp
index 35f4e38077248..70c8e474c78a6 100644
--- a/libcxxabi/src/cxa_personality.cpp
+++ b/libcxxabi/src/cxa_personality.cpp
@@ -1116,6 +1116,11 @@ __gxx_personality_seh0(PEXCEPTION_RECORD ms_exc, void *this_frame,
 
 #else
 
+#if !defined(_LIBUNWIND_VERSION)
+extern "C" _Unwind_Reason_Code __gnu_unwind_frame(_Unwind_Exception*,
+                                                  _Unwind_Context*);
+#endif
+
 // Helper function to unwind one frame.
 // ARM EHABI 7.3 and 7.4: If the personality function returns _URC_CONTINUE_UNWIND, the
 // personality routine should update the virtual register set (VRS) according to the

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[MaskRay]

__gnu_unwind_frame is a aarch32-specific function in libgcc. Is your build related to aarch32?

[planetmarshall]

__gnu_unwind_frame is a aarch32-specific function in libgcc. Is your build related to aarch32?

Armv7, yes.

[planetmarshall]

Superseded by #189787