[PATCH] D139503: [Headers][ARM] Allow `struct _Unwind_Exception` in unwind.h

[Ryan Prichard via Phabricator via cfe-commits]

rprichard added a comment.

As an aside, it seems interesting that libcxxabi/test/forced_unwind[12].pass.cpp don't compile for ARM EHABI when used with Clang's unwind.h. AFAICT it's been that way for a long time?

  $ /x/clang14/bin/clang -target arm-linux-gnueabi /x/llvm-upstream/llvm-project/libcxxabi/test/forced_unwind1.pass.cpp -c -I /x/llvm-upstream/llvm-project/libcxxabi/include
  /x/llvm-upstream/llvm-project/libcxxabi/test/forced_unwind1.pass.cpp:42:42: error: typedef '_Unwind_Exception' cannot be referenced with a struct specifier
                                    struct _Unwind_Exception*,
                                           ^
  /x/clang+llvm-14.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/14.0.0/include/unwind.h:67:38: note: declared here
  typedef struct _Unwind_Control_Block _Unwind_Exception; /* Alias */
                                       ^
  /x/llvm-upstream/llvm-project/libcxxabi/test/forced_unwind1.pass.cpp:50:49: error: typedef '_Unwind_Exception' cannot be referenced with a struct specifier
  static void cleanup(_Unwind_Reason_Code, struct _Unwind_Exception* exc) {
                                                  ^
  /x/clang+llvm-14.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/14.0.0/include/unwind.h:67:38: note: declared here
  typedef struct _Unwind_Control_Block _Unwind_Exception; /* Alias */
                                       ^
  2 errors generated.

Clang uses its own unwind.h rather than libunwind's unwind.h:

  $ /x/clang14/bin/clang -target arm-linux-gnueabi /x/llvm-upstream/llvm-project/libcxxabi/test/forced_unwind1.pass.cpp -c -I /x/llvm-upstream/llvm-project/libcxxabi/include -H 2>&1 | grep unwind.h$
  . /x/clang+llvm-14.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/14.0.0/include/unwind.h
  $ head -15 /x/clang+llvm-14.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/14.0.0/include/unwind.h
  /*===---- unwind.h - Stack unwinding ----------------------------------------===
   *
   * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   * See https://llvm.org/LICENSE.txt for license information.
   * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   *
   *===-----------------------------------------------------------------------===
   */
  
  /* See "Data Definitions for libgcc_s" in the Linux Standard Base.*/
  
  #ifndef __CLANG_UNWIND_H
  #define __CLANG_UNWIND_H
  
  #if defined(__APPLE__) && __has_include_next(<unwind.h>)


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