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[TySan] User-friendly (C style) pointer type names for error reports #166381

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[TySan] User-friendly (C style) pointer type names for error reports #166381

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[TySan] User-friendly (C style) pointer type names for error reports
BStott6 Nov 4, 2025
a71d469
Fix failing test
BStott6 Nov 4, 2025
ac99a5b
Remove command line flag, fix formatting
BStott6 Nov 6, 2025
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2 changes: 0 additions & 2 deletions clang/docs/TypeSanitizer.rst
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Expand Up @@ -119,8 +119,6 @@ brief dictionary of these terms.

* ``omnipotent char``: This is a special type which can alias with anything. Its name comes from the C/C++
type ``char``.
* ``type p[x]``: This signifies pointers to the type. ``x`` is the number of indirections to reach the final value.
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@gbMattN gbMattN Nov 4, 2025

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If we use "print tbaa name" flag then this terminology is still used, so maybe we want to keep it in the docs? Adding a note before/ after that this is no longer default behaviour would maybe be better

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@fhahn fhahn Nov 4, 2025

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I'm not sure we need the flag. Given that we print the C type name for other cases, I think it would make sense to always print the pointer in C style, and remove the flag

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@gbMattN gbMattN Nov 4, 2025

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If we are always doing C style maybe it would make sense then to change "omnipotent char" to char as well? That or change the docs to state the name is permanent

As an example, a pointer to a pointer to an integer would be ``type p2 int``.

TypeSanitizer is still experimental. User-facing error messages should be improved in the future to remove
references to LLVM IR specific terms.
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2 changes: 1 addition & 1 deletion clang/test/CodeGen/sanitize-type-globals.cpp
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Expand Up @@ -13,7 +13,7 @@
// CHECK: @__tysan_v1_omnipotent_20char = linkonce_odr constant { i64, i64, ptr, i64, [16 x i8] } { i64 2, i64 1, ptr @__tysan_v1_Simple_20C_2b_2b_20TBAA, i64 0, [16 x i8] c"omnipotent char\00" }, comdat
// CHECK: @__tysan_v1_int = linkonce_odr constant { i64, i64, ptr, i64, [4 x i8] } { i64 2, i64 1, ptr @__tysan_v1_omnipotent_20char, i64 0, [4 x i8] c"int\00" }, comdat
// CHECK: @__tysan_v1_any_20pointer = linkonce_odr constant { i64, i64, ptr, i64, [12 x i8] } { i64 2, i64 1, ptr @__tysan_v1_omnipotent_20char, i64 0, [12 x i8] c"any pointer\00" }, comdat
// CHECK: @__tysan_v1_p1_20int = linkonce_odr constant { i64, i64, ptr, i64, [7 x i8] } { i64 2, i64 1, ptr @__tysan_v1_any_20pointer, i64 0, [7 x i8] c"p1 int\00" }, comdat
// CHECK: @__tysan_v1_p1_20int = linkonce_odr constant { i64, i64, ptr, i64, [5 x i8] } { i64 2, i64 1, ptr @__tysan_v1_any_20pointer, i64 0, [5 x i8] c"int*\00" }, comdat
// CHECK: @__tysan_v1___ZTS9CompleteS = linkonce_odr constant { i64, i64, ptr, i64, ptr, i64, [15 x i8] } { i64 2, i64 2, ptr @__tysan_v1_int, i64 0, ptr @__tysan_v1_p1_20int, i64 8, [15 x i8] c"_ZTS9CompleteS\00" }, comdat
// CHECK: @__tysan_v1___ZTS1b = linkonce_odr constant { i64, i64, [7 x i8] } { i64 2, i64 0, [7 x i8] c"_ZTS1b\00" }, comdat
// CHECK: @llvm.used = appending global [8 x ptr] [ptr @tysan.module_ctor, ptr @__tysan_v1_Simple_20C_2b_2b_20TBAA, ptr @__tysan_v1_omnipotent_20char, ptr @__tysan_v1_int, ptr @__tysan_v1_any_20pointer, ptr @__tysan_v1_p1_20int, ptr @__tysan_v1___ZTS9CompleteS, ptr @__tysan_v1___ZTS1b], section "llvm.metadata"
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2 changes: 1 addition & 1 deletion compiler-rt/test/tysan/print_stacktrace.c
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Expand Up @@ -10,7 +10,7 @@ void zero_array() {
for (i = 0; i < 1; ++i)
P[i] = 0.0f;
// CHECK: ERROR: TypeSanitizer: type-aliasing-violation
// CHECK: WRITE of size 4 at {{.*}} with type float accesses an existing object of type p1 float
// CHECK: WRITE of size 4 at {{.*}} with type float accesses an existing object of type float*
// CHECK: {{#0 0x.* in zero_array .*print_stacktrace.c:}}[[@LINE-3]]
// CHECK-SHORT-NOT: {{#1 0x.* in main .*print_stacktrace.c}}
// CHECK-LONG-NEXT: {{#1 0x.* in main .*print_stacktrace.c}}
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2 changes: 1 addition & 1 deletion compiler-rt/test/tysan/ptr-float.c
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Expand Up @@ -7,7 +7,7 @@ void zero_array() {
for (i = 0; i < 1; ++i)
P[i] = 0.0f;
// CHECK: ERROR: TypeSanitizer: type-aliasing-violation
// CHECK: WRITE of size 4 at {{.*}} with type float accesses an existing object of type p1 float
// CHECK: WRITE of size 4 at {{.*}} with type float accesses an existing object of type float*
// CHECK: {{#0 0x.* in zero_array .*ptr-float.c:}}[[@LINE-3]]
}

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34 changes: 33 additions & 1 deletion llvm/lib/Transforms/Instrumentation/TypeSanitizer.cpp
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Expand Up @@ -260,6 +260,30 @@ static std::string encodeName(StringRef Name) {
return Output;
}

/// Converts pointer type names from TBAA "p2 int" style to C style ("int**").
/// Currently leaves "omnipotent char" unchanged - not sure of a user-friendly
/// name for this type. If the type name was changed, returns true and stores
/// the new type name in `Dest`. Otherwise, returns false (`Dest` is unchanged).
static bool convertTBAAStyleTypeNamesToCStyle(StringRef TypeName,
std::string &Dest) {
if (!TypeName.consume_front("p"))
return false;

int Indirection;
if (TypeName.consumeInteger(10, Indirection))
return false;

if (!TypeName.consume_front(" "))
return false;

Dest.clear();
Dest.reserve(TypeName.size() + Indirection); // One * per indirection
Dest.append(TypeName);
Dest.append(Indirection, '*');

return true;
}

std::string
TypeSanitizer::getAnonymousStructIdentifier(const MDNode *MD,
TypeNameMapTy &TypeNames) {
Expand Down Expand Up @@ -355,7 +379,15 @@ bool TypeSanitizer::generateBaseTypeDescriptor(
// [2, member count, [type pointer, offset]..., name]

LLVMContext &C = MD->getContext();
Constant *NameData = ConstantDataArray::getString(C, NameNode->getString());
StringRef TypeName = NameNode->getString();

// Convert LLVM-internal TBAA-style type names to C-style type names
// (more user-friendly)
std::string CStyleTypeName;
if (convertTBAAStyleTypeNamesToCStyle(TypeName, CStyleTypeName))
TypeName = CStyleTypeName;

Constant *NameData = ConstantDataArray::getString(C, TypeName);
SmallVector<Type *> TDSubTys;
SmallVector<Constant *> TDSubData;

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