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[Clang] Add diagnostic about "%P" specifier with Objective-C pointers #89977

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Merged
merged 1 commit into from
Apr 29, 2024
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[Clang] Add diagnostic about "%P" specifier with Objective-C pointers #89977

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3 changes: 3 additions & 0 deletions clang/include/clang/Basic/DiagnosticSemaKinds.td
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Original file line number Diff line number Diff line change
Expand Up @@ -9901,6 +9901,9 @@ def warn_format_invalid_annotation : Warning<
def warn_format_P_no_precision : Warning<
"using '%%P' format specifier without precision">,
InGroup<Format>;
def warn_format_P_with_objc_pointer : Warning<
"using '%%P' format specifier with an Objective-C pointer results in dumping runtime object structure, not object value">,
InGroup<Format>;
def warn_printf_ignored_flag: Warning<
"flag '%0' is ignored when flag '%1' is present">,
InGroup<Format>;
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11 changes: 11 additions & 0 deletions clang/lib/Sema/SemaChecking.cpp
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Expand Up @@ -12544,6 +12544,17 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
return true;
}

// Diagnose attempts to use '%P' with ObjC object types, which will result in
// dumping raw class data (like is-a pointer), not actual data.
if (FS.getConversionSpecifier().getKind() == ConversionSpecifier::PArg &&
ExprTy->isObjCObjectPointerType()) {
const CharSourceRange &CSR =
getSpecifierRange(StartSpecifier, SpecifierLen);
EmitFormatDiagnostic(S.PDiag(diag::warn_format_P_with_objc_pointer),
E->getExprLoc(), false, CSR);
return true;
}

ArgType::MatchKind ImplicitMatch = ArgType::NoMatch;
ArgType::MatchKind Match = AT.matchesType(S.Context, ExprTy);
ArgType::MatchKind OrigMatch = Match;
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5 changes: 4 additions & 1 deletion clang/test/SemaObjC/format-strings-oslog.m
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Expand Up @@ -44,15 +44,18 @@ void test_os_log_format(const char *pc, int i, void *p, void *buf) {
}

// Test os_log_format primitive with ObjC string literal format argument.
void test_objc(const char *pc, int i, void *p, void *buf, NSString *nss) {
void test_objc(const char *pc, int i, void *p, void *buf, NSString *nss, id obj) {
__builtin_os_log_format(buf, @"");
__builtin_os_log_format(buf, @"%d"); // expected-warning {{more '%' conversions than data arguments}}
__builtin_os_log_format(buf, @"%d", i);

__builtin_os_log_format(buf, @"%P", p); // expected-warning {{using '%P' format specifier without precision}}
__builtin_os_log_format(buf, @"%.10P", p);
__builtin_os_log_format(buf, @"%.*P", p); // expected-warning {{field precision should have type 'int', but argument has type 'void *'}}
__builtin_os_log_format(buf, @"%.*P", i, p);
__builtin_os_log_format(buf, @"%.*P", i, i); // expected-warning {{format specifies type 'void *' but the argument has type 'int'}}
__builtin_os_log_format(buf, @"%.8P", nss); // expected-warning {{using '%P' format specifier with an Objective-C pointer results in dumping runtime object structure, not object value}}
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Should it warn when (void *)nss is passed too?

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I don't think so, but I can be convinced. IMO, using a (void*) cast could be the escape-hatch if someone actually really does want to dump the ObjC runtime structure but also squash this warning.

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Yes, that makes sense.

__builtin_os_log_format(buf, @"%.*P", i, obj); // expected-warning {{using '%P' format specifier with an Objective-C pointer results in dumping runtime object structure, not object value}}

__builtin_os_log_format(buf, @"%{private}s", pc);
__builtin_os_log_format(buf, @"%@", nss);
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