[cfe-dev] multi-dimensional char arrays

[Chris Lattner]

On Dec 16, 2007, at 7:04 AM, Steve Naroff wrote:
> fyi...clang's initializer support is still incomplete (e.g. we still  
> don't support structures).  Back in September, I added some basic  
> support that implements ~85% of the C99 spec. Since then, Anders and  
> I made some tweaks for supporting "basic" character arrays (which  
> doesn't correctly handle the case below).
>
> I hope to finish initializer support after the holidays.

In the meantime, enough people are hitting the codegen assertion that  
I added a hack to the code generator to warn about it and carry on.   
You'll get invalid code, but at least you won't get crashes all over  
the place:

t3.c:1:24: warning: cannot codegen this initializer yet
const char x[2][4] = { { 'a', 'b', '\0', '\0' }, { 'c', 'd', 'e',  
'\0' } };
                        ^~~~~~~~~~~~~~~~~~~~~~~~

-Chris

> snaroff
>
> On Dec 16, 2007, at 6:04 AM, Shantonu Sen wrote:
>
>> The following source fails to parse:
>>
>> $ cat a.c
>> const char w[4] = "ab";
>> const char x[2][4] = { { 'a', 'b', '\0', '\0' }, { 'c', 'd', 'e',  
>> '\0' } };
>> const char y[2][4] = { "ab", "cde" };
>> const char y2[2][4] = { { "ab" }, { "cde" } };
>> const char * const z[2] = { "ab", "cde" };
>> ]$ clang -std=c99 a.c -fsyntax-only
>> a.c:3:30: error: excess elements in char array initializer
>> const char y[2][4] = { "ab", "cde" };
>>                              ^~~~~
>> 1 diagnostic generated.
>> $
>>
>> This appears to be C99 6.7.8.14:
>>
>>> 14 An array of character type may be initialized by a character  
>>> string literal, optionally
>>> enclosed in braces. Successive characters of the character string  
>>> literal (including the
>>> terminating null character if there is room or if the array is of  
>>> unknown size) initialize the
>>> elements of the array.
>>
>> Additionally, even when compiling just "x", -emit-llvm fails:
>> $ cat b.c
>> const char x[2][4] = { { 'a', 'b', '\0', '\0' }, { 'c', 'd', 'e',  
>> '\0' } };
>> $ clang -std=c99 b.c -ast-dump
>> typedef char *__builtin_va_list;
>> Read top-level variable decl: 'x'
>> $ clang -std=c99 b.c -emit-llvm 2>&1 | c++filt -n
>> Assertion failed: (ILE->getType()->isArrayType() || ILE->getType()- 
>> >isStructureType()), function GenerateAggregateInit, file  
>> CodeGenModule.cpp, line 284.
>> 0   clang                               0x0021b8cb (anonymous  
>> namespace)::PrintStackTrace() + 45
>> 1   clang                               0x0021bc71 (anonymous  
>> namespace)::SignalHandler(int) + 323
>> 2   libSystem.B.dylib                   0x9188897b _sigtramp + 43
>> 3   ???                                 0xffffffff 0x0 + 4294967295
>> 4   libSystem.B.dylib                   0x91901782 raise + 26
>> 5   libSystem.B.dylib                   0x91910d3f abort + 73
>> 6   libSystem.B.dylib                   0x91902923 __assert_rtn + 101
>> 7   clang                               0x0005d9a1  
>> clang 
>> ::CodeGen 
>> ::CodeGenModule::GetAddrOfConstantCFString(std::basic_string<char,  
>> std::char_traits<char>, std::allocator<char> > const&) + 1577
>> 8   clang                               0x0005e4ce  
>> clang 
>> ::CodeGen 
>> ::CodeGenModule::GetAddrOfConstantCFString(std::basic_string<char,  
>> std::char_traits<char>, std::allocator<char> > const&) + 4438
>> 9   clang                               0x0005dae3  
>> clang 
>> ::CodeGen 
>> ::CodeGenModule::GetAddrOfConstantCFString(std::basic_string<char,  
>> std::char_traits<char>, std::allocator<char> > const&) + 1899
>> 10  clang                               0x0005e4ce  
>> clang 
>> ::CodeGen 
>> ::CodeGenModule::GetAddrOfConstantCFString(std::basic_string<char,  
>> std::char_traits<char>, std::allocator<char> > const&) + 4438
>> 11  clang                               0x0005e53e  
>> clang::CodeGen::CodeGenModule::EmitGlobalInit(clang::Expr const*) +  
>> 24
>> 12  clang                               0x0005e6d6  
>> clang::CodeGen::CodeGenModule::EmitGlobalVar(clang::FileVarDecl  
>> const*) + 406
>> 13  clang                               0x0005e7e6  
>> clang 
>> ::CodeGen 
>> ::CodeGenModule::EmitGlobalVarDeclarator(clang::FileVarDecl const*)  
>> + 26
>> 14  clang                               0x00067ddc  
>> clang::CodeGen::CodeGenGlobalVar(clang::CodeGen::CodeGenModule*,  
>> clang::FileVarDecl*) + 24
>> 15  clang                               0x00006229 (anonymous  
>> namespace)::LLVMEmitter::HandleTopLevelDecl(clang::Decl*) + 119
>> 16  clang                               0x0007af58  
>> clang::ParseAST(clang::Preprocessor&, unsigned int,  
>> clang::ASTConsumer*, bool) + 258
>> 17  clang                               0x000222c2  
>> llvm::BitstreamWriter::Emit(unsigned int, unsigned int) + 3740
>> 18  clang                               0x0002444e main + 1370
>> 19  clang                               0x00001cca start + 54
>>
>>
>> Shantonu Sen
>> ssen at apple.com
>>
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
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