[PATCH] Error out of ParseBitcodeInto(Module*) if we haven't read a Module

[Duncan Exon Smith]

> On Apr 14, 2015, at 6:00 AM, Filipe Cabecinhas <filcab+llvm.phabricator at gmail.com> wrote:
> 
> Hi dexonsmith, rafael,
> 
> Without this check the following case failed:
> 
> Skip a SubBlock which is not a MODULE_BLOCK_ID nor a BLOCKINFO_BLOCK_ID
> Got to end of file
> 
> TheModule would still be == nullptr, and we would subsequentially fail
> when materializing the Module (assert at the start of
> BitcodeReader::MaterializeModule).
> 
> Bug found with AFL.
> 
> http://reviews.llvm.org/D9014

LGTM with one whitespace nit. 

> 
> Files:
> lib/Bitcode/Reader/BitcodeReader.cpp
> test/Bitcode/Inputs/invalid-no-proper-module.bc
> test/Bitcode/invalid.test
> 
> Index: lib/Bitcode/Reader/BitcodeReader.cpp
> ===================================================================
> --- lib/Bitcode/Reader/BitcodeReader.cpp
> +++ lib/Bitcode/Reader/BitcodeReader.cpp
> @@ -3063,8 +3063,12 @@
>  // We expect a number of well-defined blocks, though we don't necessarily
>  // need to understand them all.
>  while (1) {
> -    if (Stream.AtEndOfStream())
> -      return std::error_code();
> +    if (Stream.AtEndOfStream()) {
> +      if (TheModule)
> +        return std::error_code();
> +      // We didn't really read a proper Module

Period (".") at the end of the sentence. 

> +      return Error("Malformed IR file");
> +    }
> 
>    BitstreamEntry Entry =
>      Stream.advance(BitstreamCursor::AF_DontAutoprocessAbbrevs);
> Index: test/Bitcode/invalid.test
> ===================================================================
> --- test/Bitcode/invalid.test
> +++ test/Bitcode/invalid.test
> @@ -50,3 +50,8 @@
> INSERT-ARRAY: INSERTVAL: Invalid array index
> INSERT-STRUCT: INSERTVAL: Invalid struct index
> INSERT-IDXS: INSERTVAL: Invalid type
> +
> +RUN: not llvm-dis -disable-output %p/Inputs/invalid-no-proper-module.bc 2>&1 | \
> +RUN:   FileCheck --check-prefix=NO-MODULE %s
> +
> +NO-MODULE: Malformed IR file
> 
> EMAIL PREFERENCES
> http://reviews.llvm.org/settings/panel/emailpreferences/
> <D9014.23729.patch>