https://github.com/jaredgrubb created
https://github.com/llvm/llvm-project/pull/89977
A Darwin extension '%P' combined with an Objective-C pointer seems to always be
a bug.
'%P' will dump bytes at the pointed-to address (in contrast to '%p' which dumps
the pointer itself). This extension is only allowed in "OS Log" contexts and is
intended to be used like `%{uuid_t}.*16P` or `%{timeval}.*P`. If an ObjC
pointer is used, then the internal runtime structure (aka, the is-a pointer and
other runtime metadata) will be dumped, which (IMO) is never the expectation.
A simple diagnostic can help flag these scenarios.
>From 1d8e6a51d6df6ea760e5c857fffcfae238932091 Mon Sep 17 00:00:00 2001
From: Jared Grubb
Date: Wed, 24 Apr 2024 12:05:20 -0700
Subject: [PATCH] [Clang] Add diagnostic to flag using "%P" specifier with
Objective-C pointers (#89968)
A Darwin extension '%P' combined with an Objective-C pointer seems to always be
a
bug.
'%P' will dump bytes at the pointed-to address (in contrast to '%p' which dumps
the pointer itself). This extension is only allowed in "OS Log" contexts and is
intended
to be used like `%{uuid_t}.*16P` or `%{timeval}.*P`. If an ObjC pointer is used,
then the internal runtime structure (aka, the is-a pointer and other runtime
metadata)
will be dumped, which (IMO) is never the expectation.
A simple diagnostic can help flag these scenarios.
---
clang/include/clang/Basic/DiagnosticSemaKinds.td | 3 +++
clang/lib/Sema/SemaChecking.cpp | 11 +++
clang/test/SemaObjC/format-strings-oslog.m | 5 -
3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 6732a1a98452ad..d7de9cf2c86e0e 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -9901,6 +9901,9 @@ def warn_format_invalid_annotation : Warning<
def warn_format_P_no_precision : Warning<
"using '%%P' format specifier without precision">,
InGroup;
+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;
def warn_printf_ignored_flag: Warning<
"flag '%0' is ignored when flag '%1' is present">,
InGroup;
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 67132701b41cfd..53dbd58b0252a2 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -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;
diff --git a/clang/test/SemaObjC/format-strings-oslog.m
b/clang/test/SemaObjC/format-strings-oslog.m
index 20fec93b653bd5..af5aef3d617954 100644
--- a/clang/test/SemaObjC/format-strings-oslog.m
+++ b/clang/test/SemaObjC/format-strings-oslog.m
@@ -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}}
+ __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,
