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Format strings: a character literal should be printed with %c, not %d. 

The type of a character literal is 'int' in C, but if the user writes a
character /as/ a literal, we should assume they meant it to be a
character and not a numeric value, and thus offer %c as a correction
rather than %d.

There's a special case for multi-character literals (like 'MooV'), which
have implementation-defined value and usually cannot be printed with %c.
These still use %d as the suggestion.

In C++, the type of a character literal is 'char', and so this problem
doesn't exist.

<rdar://problem/12282316>

llvm-svn: 169398
This commit is contained in:
Jordan Rose 2012-12-05 18:44:40 +00:00
parent 6aaa87e0d2
commit 598ec0992d
2 changed files with 51 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
clang/lib/Sema/SemaChecking.cpp
View File

@ -2717,8 +2717,8 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
if (!AT.isValid())
return true;
QualType IntendedTy = E->getType();
if (AT.matchesType(S.Context, IntendedTy))
QualType ExprTy = E->getType();
if (AT.matchesType(S.Context, ExprTy))
return true;
// Look through argument promotions for our error message's reported type.
@ -2729,7 +2729,7 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
if (ICE->getCastKind() == CK_IntegralCast ||
ICE->getCastKind() == CK_FloatingCast) {
E = ICE->getSubExpr();
IntendedTy = E->getType();
ExprTy = E->getType();
// Check if we didn't match because of an implicit cast from a 'char'
// or 'short' to an 'int'. This is done because printf is a varargs
@ -2737,12 +2737,20 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
if (ICE->getType() == S.Context.IntTy ||
ICE->getType() == S.Context.UnsignedIntTy) {
// All further checking is done on the subexpression.
if (AT.matchesType(S.Context, IntendedTy))
if (AT.matchesType(S.Context, ExprTy))
return true;
}
}
} else if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E)) {
// Special case for 'a', which has type 'int' in C.
// Note, however, that we do /not/ want to treat multibyte constants like
// 'MooV' as characters! This form is deprecated but still exists.
if (ExprTy == S.Context.IntTy)
if (llvm::isUIntN(S.Context.getCharWidth(), CL->getValue()))
ExprTy = S.Context.CharTy;
}
QualType IntendedTy = ExprTy;
if (S.Context.getTargetInfo().getTriple().isOSDarwin()) {
// Special-case some of Darwin's platform-independence types.
if (const TypedefType *UserTy = IntendedTy->getAs<TypedefType>()) {
@ -2769,7 +2777,7 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
CharSourceRange SpecRange = getSpecifierRange(StartSpecifier, SpecifierLen);
if (IntendedTy != E->getType()) {
if (IntendedTy != ExprTy) {
// The canonical type for formatting this value is different from the
// actual type of the expression. (This occurs, for example, with Darwin's
// NSInteger on 32-bit platforms, where it is typedef'd as 'int', but
@ -2809,7 +2817,7 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
// We extract the name from the typedef because we don't want to show
// the underlying type in the diagnostic.
const TypedefType *UserTy = cast<TypedefType>(E->getType());
const TypedefType *UserTy = cast<TypedefType>(ExprTy);
StringRef Name = UserTy->getDecl()->getName();
// Finally, emit the diagnostic.
@ -2834,9 +2842,9 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
// Since the warning for passing non-POD types to variadic functions
// was deferred until now, we emit a warning for non-POD
// arguments here.
if (S.isValidVarArgType(E->getType()) == Sema::VAK_Invalid) {
if (S.isValidVarArgType(ExprTy) == Sema::VAK_Invalid) {
unsigned DiagKind;
if (E->getType()->isObjCObjectType())
if (ExprTy->isObjCObjectType())
DiagKind = diag::err_cannot_pass_objc_interface_to_vararg_format;
else
DiagKind = diag::warn_non_pod_vararg_with_format_string;
@ -2844,7 +2852,7 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
EmitFormatDiagnostic(
S.PDiag(DiagKind)
<< S.getLangOpts().CPlusPlus0x
<< E->getType()
<< ExprTy
<< CallType
<< AT.getRepresentativeTypeName(S.Context)
<< CSR
@ -2855,7 +2863,7 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
} else
EmitFormatDiagnostic(
S.PDiag(diag::warn_printf_conversion_argument_type_mismatch)
<< AT.getRepresentativeTypeName(S.Context) << E->getType()
<< AT.getRepresentativeTypeName(S.Context) << ExprTy
<< CSR
<< E->getSourceRange(),
E->getLocStart(), /*IsStringLocation*/false, CSR);

33
clang/test/FixIt/format.m
View File

@ -146,4 +146,37 @@ void test_char(char c, signed char s, unsigned char u, uint8_t n) {
NSLog(@"%c", n); // no-warning
// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%hhu"
NSLog(@"%s", 'a'); // expected-warning{{format specifies type 'char *' but the argument has type 'char'}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%c"
NSLog(@"%lf", 'a'); // expected-warning{{format specifies type 'double' but the argument has type 'char'}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:14}:"%c"
NSLog(@"%@", 'a'); // expected-warning{{format specifies type 'id' but the argument has type 'char'}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%c"
NSLog(@"%c", 'a'); // no-warning
// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%c"
NSLog(@"%s", 'abcd'); // expected-warning{{format specifies type 'char *' but the argument has type 'int'}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%d"
NSLog(@"%lf", 'abcd'); // expected-warning{{format specifies type 'double' but the argument has type 'int'}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:14}:"%d"
NSLog(@"%@", 'abcd'); // expected-warning{{format specifies type 'id' but the argument has type 'int'}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%d"
}
void multichar_constants_false_negative() {
// The value of a multi-character constant is implementation-defined, but
// almost certainly shouldn't be printed with %c. However, the current
// type-checker expects %c to correspond to an integer argument, because
// many C library functions like fgetc() actually return an int (using -1
// as a sentinel).
NSLog(@"%c", 'abcd'); // missing-warning{{format specifies type 'char' but the argument has type 'int'}}
// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:11-[[@LINE-1]]:13}:"%d"
}