[llvm] r175063 - [ms-inline-asm] Use an array_pod_sort, rather than a std:sort.

[Timur Iskhodzhanov]

OK, here we go.

The crash happens if you "#include <windows.h>" on a machine with
VS2010 installed (other versions might be affected too).

Here's a patch that adds an assert that crashes:
---------------------------------------------------------------------------------
diff --git lib/MC/MCParser/AsmParser.cpp lib/MC/MCParser/AsmParser.cpp
index 2cce8b0..1cfd5f6 100644
--- lib/MC/MCParser/AsmParser.cpp
+++ lib/MC/MCParser/AsmParser.cpp
@@ -4174,8 +4174,10 @@ bool AsmParser::ParseMSInlineAsm(void *AsmLoc,
std::string &AsmString,

     // Emit everything up to the immediate/expression.  If the previous rewrite
     // was a size directive, then this has already been done.
-    if (PrevKind != AOK_SizeDirective)
+    if (PrevKind != AOK_SizeDirective) {
+      assert(Loc >= Start);
       OS << StringRef(Start, Loc - Start);
+    }
     PrevKind = Kind;

     // Skip the original expression.
---------------------------------------------------------------------------------


I hope that's enough info to debug :)


FYI The bug was hard to debug as a substantial part of memory was
corrupted (including EBPs, return addresses etc)
so I propose something like this to prevent such bugs from re-appearing:
---------------------------------------------------------------------------------
diff --git include/llvm/ADT/StringRef.h include/llvm/ADT/StringRef.h
index 1e21d92..077c056 100644
--- include/llvm/ADT/StringRef.h
+++ include/llvm/ADT/StringRef.h
@@ -84,6 +84,7 @@ namespace llvm {
       : Data(data), Length(length) {
         assert((data || length == 0) &&
         "StringRef cannot be built from a NULL argument with non-null length");
+        assert(length < 0x80000000 && "length looks suspicious");
       }

     /// Construct a string ref from an std::string.
---------------------------------------------------------------------------------

2013/2/15 Timur Iskhodzhanov <timurrrr at google.com>:
> FYI this crashes on my Windows bot.
>
> I'll update with the details when I reproduce locally.
>
> 2013/2/13 Chad Rosier <mcrosier at apple.com>:
>> Author: mcrosier
>> Date: Wed Feb 13 12:38:58 2013
>> New Revision: 175063
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=175063&view=rev
>> Log:
>> [ms-inline-asm] Use an array_pod_sort, rather than a std:sort.
>>
>>
>> Modified:
>>     llvm/trunk/lib/MC/MCParser/AsmParser.cpp
>>
>> Modified: llvm/trunk/lib/MC/MCParser/AsmParser.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCParser/AsmParser.cpp?rev=175063&r1=175062&r2=175063&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/MC/MCParser/AsmParser.cpp (original)
>> +++ llvm/trunk/lib/MC/MCParser/AsmParser.cpp Wed Feb 13 12:38:58 2013
>> @@ -13,6 +13,7 @@
>>
>>  #include "llvm/ADT/APFloat.h"
>>  #include "llvm/ADT/SmallString.h"
>> +#include "llvm/ADT/STLExtras.h"
>>  #include "llvm/ADT/StringMap.h"
>>  #include "llvm/ADT/Twine.h"
>>  #include "llvm/MC/MCAsmInfo.h"
>> @@ -4029,8 +4030,14 @@ bool AsmParser::ParseDirectiveMSAlign(SM
>>    return false;
>>  }
>>
>> -bool AsmStringSort (AsmRewrite A, AsmRewrite B) {
>> -  return A.Loc.getPointer() < B.Loc.getPointer();
>> +static int RewritesSort (const void *A, const void *B) {
>> +  const AsmRewrite *AsmRewriteA = static_cast<const AsmRewrite*>(A);
>> +  const AsmRewrite *AsmRewriteB = static_cast<const AsmRewrite*>(B);
>> +  if (AsmRewriteA->Loc.getPointer() < AsmRewriteB->Loc.getPointer())
>> +    return -1;
>> +  if (AsmRewriteB->Loc.getPointer() < AsmRewriteA->Loc.getPointer())
>> +    return 1;
>> +  return 0;
>>  }
>>
>>  bool AsmParser::ParseMSInlineAsm(void *AsmLoc, std::string &AsmString,
>> @@ -4157,7 +4164,7 @@ bool AsmParser::ParseMSInlineAsm(void *A
>>    AsmRewriteKind PrevKind = AOK_Imm;
>>    raw_string_ostream OS(AsmStringIR);
>>    const char *Start = SrcMgr.getMemoryBuffer(0)->getBufferStart();
>> -  std::sort (AsmStrRewrites.begin(), AsmStrRewrites.end(), AsmStringSort);
>> +  array_pod_sort (AsmStrRewrites.begin(), AsmStrRewrites.end(), RewritesSort);
>>    for (SmallVectorImpl<struct AsmRewrite>::iterator
>>           I = AsmStrRewrites.begin(), E = AsmStrRewrites.end(); I != E; ++I) {
>>      const char *Loc = (*I).Loc.getPointer();
>>
>>
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