On Sun, May 5, 2013 at 8:45 AM, Abramo Bagnara <[email protected]>wrote:
> Il 05/05/2013 17:05, Richard Smith ha scritto: > > On Sun, May 5, 2013 at 2:53 AM, Abramo Bagnara > > <[email protected] <mailto:[email protected]>> wrote: > > > > Il 26/04/2013 16:36, Richard Smith ha scritto: > > > Modified: cfe/trunk/lib/Sema/SemaInit.cpp > > > URL: > > > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=180603&r1=180602&r2=180603&view=diff > > > > > > ============================================================================== > > > --- cfe/trunk/lib/Sema/SemaInit.cpp (original) > > > +++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Apr 26 09:36:30 2013 > > > @@ -97,6 +97,7 @@ static void CheckStringInit(Expr *Str, Q > > > DeclT = S.Context.getConstantArrayType(IAT->getElementType(), > > > ConstVal, > > > ArrayType::Normal, 0); > > > + Str->setType(DeclT); > > > return; > > > } > > > > Is this change deliberate? It seems to introduce a regression: > > > > $ cat z.c > > > > void f() { > > signed char s[] = "a"; > > unsigned char u[] = "a"; > > } > > $ _clang -cc1 -ast-dump z.c > > TranslationUnitDecl 0x67d96e0 <<invalid sloc>> > > |-TypedefDecl 0x67d9bc0 <<invalid sloc>> __int128_t '__int128' > > |-TypedefDecl 0x67d9c20 <<invalid sloc>> __uint128_t 'unsigned > __int128' > > |-TypedefDecl 0x67d9f70 <<invalid sloc>> __builtin_va_list > > '__va_list_tag [1]' > > `-FunctionDecl 0x67da010 <z.c:2:1, line:5:1> f 'void ()' > > `-CompoundStmt 0x67da350 <line:2:10, line:5:1> > > |-DeclStmt 0x67da208 <line:3:3, col:24> > > | `-VarDecl 0x67da100 <col:3, col:21> s 'signed char [2]' > > | `-StringLiteral 0x67da198 <col:21> 'signed char [2]' lvalue > "a" > > `-DeclStmt 0x67da338 <line:4:3, col:26> > > `-VarDecl 0x67da270 <col:3, col:23> u 'unsigned char [2]' > > `-StringLiteral 0x67da2c8 <col:23> 'unsigned char [2]' > > lvalue "a" > > > > Type of string literal should be plain char. > > > > > > Yes, this is deliberate; we intended to set the string literal's type to > > the type of the initialized variable (otherwise we would be initializing > > an array of 'unsigned char' from an array of 'char'), but accidentally > > only updated it in either the array bound or the type, but not both. > > > > unsigned char a[] = "foo", b[4] = "bar"; > > > > ... used to produce ... > > > > |-VarDecl 0x6222ad0 <<stdin>:1:1, col:21> a 'unsigned char [4]' > > | `-StringLiteral 0x6222ba8 <col:21> 'const char [4]' lvalue "foo" > > `-VarDecl 0x6222c60 <col:1, col:35> b 'unsigned char [4]' > > `-StringLiteral 0x6222cb8 <col:35> 'unsigned char [4]' lvalue "bar" > > BTW: uniformity is still not there: > $ cat z.c > void f() { > unsigned char q[] = ("a"); > } > $ _clang -cc1 -ast-dump z.c > TranslationUnitDecl 0x6f296e0 <<invalid sloc>> > |-TypedefDecl 0x6f29bc0 <<invalid sloc>> __int128_t '__int128' > |-TypedefDecl 0x6f29c20 <<invalid sloc>> __uint128_t 'unsigned __int128' > |-TypedefDecl 0x6f29f70 <<invalid sloc>> __builtin_va_list > '__va_list_tag [1]' > `-FunctionDecl 0x6f2a010 <z.c:2:1, line:4:1> f 'void ()' > `-CompoundStmt 0x6f2a240 <line:2:10, line:4:1> > `-DeclStmt 0x6f2a228 <line:3:3, col:28> > `-VarDecl 0x6f2a100 <col:3, col:27> q 'unsigned char [2]' > `-ParenExpr 0x6f2a1c8 <col:23, col:27> 'unsigned char [2]' lvalue > `-StringLiteral 0x6f2a198 <col:24> 'char [2]' lvalue "a" > Yes, this is definitely wrong. A ParenExpr shouldn't change the type of its operand. IMHO the type of StringLiteral and ParenExpr should be char[] and as the > use of string literal for array initialization is definitely a special > case, nothing is wrong if its type is the one mandated by the standard > and different from initialized decl (i.e. "initialize this unsigned char > array from this byte sequence that is plain char typed") There are several problems with that approach (or one problem viewed in several different ways): - it introduces a change in type with no AST node performing the conversion - the StringLiteral expression actually *is* creating an object of type unsigned char[2] in this case - in C++, the standard-mandated type is *const* char[N], but such a StringLiteral can still be the value of a non-const array Analogous to how we handle InitListExprs, we could keep separate syntactic and semantic forms for a StringLiteral used as an initializer (or maybe just separate syntactic and semantic types).
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