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[clang][bytecode] Check memcmp builtin for one-past-the-end pointers #170097

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Merged
tbaederr merged 1 commit into from
Dec 1, 2025
Merged

[clang][bytecode] Check memcmp builtin for one-past-the-end pointers #170097

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4 changes: 4 additions & 0 deletions clang/lib/AST/ByteCode/InterpBuiltin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1921,6 +1921,10 @@ static bool interp__builtin_memcmp(InterpState &S, CodePtr OpPC,
if (PtrA.isDummy() || PtrB.isDummy())
return false;

if (!CheckRange(S, OpPC, PtrA, AK_Read) ||
!CheckRange(S, OpPC, PtrB, AK_Read))
return false;

// Now, read both pointers to a buffer and compare those.
BitcastBuffer BufferA(
Bits(ASTCtx.getTypeSize(ElemTypeA) * PtrA.getNumElems()));
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7 changes: 7 additions & 0 deletions clang/test/AST/ByteCode/builtin-functions.cpp
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Expand Up @@ -1545,6 +1545,13 @@ namespace Memcmp {

int unknown;
void foo(void) { unknown *= __builtin_memcmp(0, 0, 2); }

constexpr int onepasttheend(char a) {
__builtin_memcmp(&a, &a + 1, 1); // both-note {{read of dereferenced one-past-the-end pointer}}
return 1;
}
static_assert(onepasttheend(10)); // both-error {{not an integral constant expression}} \
// both-note {{in call to}}
}

namespace Memchr {
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