[llvm] r239227 - [MC] Common symbols weren't being checked for redeclaration which allowed an assembly file to generate an assertion in setCommon(): !isCommon(). This change allows redeclaration as long as the size and alignment match exactly, otherwise report a fatal error.

[Rafael Espíndola]

This fixes https://llvm.org/bugs/show_bug.cgi?id=23621, no?

Thanks,
Rafael


On 6 June 2015 at 16:12, Colin LeMahieu <colinl at codeaurora.org> wrote:
> Author: colinl
> Date: Sat Jun  6 15:12:40 2015
> New Revision: 239227
>
> URL: http://llvm.org/viewvc/llvm-project?rev=239227&view=rev
> Log:
> [MC] Common symbols weren't being checked for redeclaration which allowed an assembly file to generate an assertion in setCommon(): !isCommon().  This change allows redeclaration as long as the size and alignment match exactly, otherwise report a fatal error.
>
> Added:
>     llvm/trunk/test/MC/ELF/common-error3.s
>     llvm/trunk/test/MC/ELF/common-redeclare.s
> Modified:
>     llvm/trunk/include/llvm/MC/MCSymbol.h
>     llvm/trunk/lib/MC/MCELFStreamer.cpp
>
> Modified: llvm/trunk/include/llvm/MC/MCSymbol.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSymbol.h?rev=239227&r1=239226&r2=239227&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCSymbol.h (original)
> +++ llvm/trunk/include/llvm/MC/MCSymbol.h Sat Jun  6 15:12:40 2015
> @@ -258,6 +258,21 @@ public:
>      return CommonAlign;
>    }
>
> +  /// Declare this symbol as being 'common'.
> +  ///
> +  /// \param Size - The size of the symbol.
> +  /// \param Align - The alignment of the symbol.
> +  /// \return True if symbol was already declared as a different type
> +  bool declareCommon(uint64_t Size, unsigned Align) {
> +    assert(isCommon() || getOffset() == 0);
> +    if(isCommon()) {
> +      if(CommonSize != Size || CommonAlign != Align)
> +       return true;
> +    } else
> +      setCommon(Size, Align);
> +    return false;
> +  }
> +
>    /// Is this a 'common' symbol.
>    bool isCommon() const { return CommonAlign != -1U; }
>
>
> Modified: llvm/trunk/lib/MC/MCELFStreamer.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCELFStreamer.cpp?rev=239227&r1=239226&r2=239227&view=diff
> ==============================================================================
> --- llvm/trunk/lib/MC/MCELFStreamer.cpp (original)
> +++ llvm/trunk/lib/MC/MCELFStreamer.cpp Sat Jun  6 15:12:40 2015
> @@ -320,7 +320,9 @@ void MCELFStreamer::EmitCommonSymbol(MCS
>      struct LocalCommon L = {Symbol, Size, ByteAlignment};
>      LocalCommons.push_back(L);
>    } else {
> -    Symbol->setCommon(Size, ByteAlignment);
> +    if(Symbol->declareCommon(Size, ByteAlignment))
> +      report_fatal_error("Symbol: " + Symbol->getName() +
> +                         " redeclared as different type");
>    }
>
>    cast<MCSymbolELF>(Symbol)
>
> Added: llvm/trunk/test/MC/ELF/common-error3.s
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/common-error3.s?rev=239227&view=auto
> ==============================================================================
> --- llvm/trunk/test/MC/ELF/common-error3.s (added)
> +++ llvm/trunk/test/MC/ELF/common-error3.s Sat Jun  6 15:12:40 2015
> @@ -0,0 +1,5 @@
> +# RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux %s 2>&1 | FileCheck %s
> +
> +# CHECK: Symbol: C redeclared as different type
> +        .comm   C,4,4
> +        .comm   C,8,4
> \ No newline at end of file
>
> Added: llvm/trunk/test/MC/ELF/common-redeclare.s
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/common-redeclare.s?rev=239227&view=auto
> ==============================================================================
> --- llvm/trunk/test/MC/ELF/common-redeclare.s (added)
> +++ llvm/trunk/test/MC/ELF/common-redeclare.s Sat Jun  6 15:12:40 2015
> @@ -0,0 +1,5 @@
> +# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux %s | llvm-objdump -t - | FileCheck %s
> +
> +# CHECK: 0000000000000004 g       *COM*  00000004 C
> +        .comm   C,4,4
> +        .comm   C,4,4
> \ No newline at end of file
>
>
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