[llvm-bugs] [Bug 40322] New: clang generates incorrect unwind information on 32-bit mingw

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40322

            Bug ID: 40322
           Summary: clang generates incorrect unwind information on 32-bit
                    mingw
           Product: new-bugs
           Version: 7.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: marc at groundctl.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

Created attachment 21330
  --> https://bugs.llvm.org/attachment.cgi?id=21330&action=edit
attached program

When compiling the attached program with the arguments "-target
i686-w64-mingw32 -O2", the resulting executable aborts.  When compiling with
"-target i686-w64-mingw32 -O0" the executable works correctly.

This appears to be because the generated dwarf unwind information is incorrect.
 When the unwinder looks for the return address of "am" it is off by 4 bytes
and finds the argument to "am", which is 0, and so it thinks the stack has
ended.

I am using the current Arch Linux clang build, version "7.0.1
(tags/RELEASE_701/final)".  This does not happen when targeting
"x86_64-w64-mingw32".  This does not happen when using -O1.

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