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[Wunsafe-buffer-usage] Address some false positives in handling array indices that are decidably correct #117370

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[Wunsafe-buffer-usage] Address some false positives in handling array indices that are decidably correct #117370

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8fed333
[Wunsafe-buffer-usage] Fix false positives in handling enums
Nov 22, 2024
35207ea
Detect when the buffer is a member access, fix tests
Nov 23, 2024
f534ebe
Fix test for unsafe enum
Nov 23, 2024
3cdadc6
Minor nit, reorder expression
Nov 25, 2024
2ffd0df
Try harder to find an element we can analyze
Nov 25, 2024
c1cfa18
Remove integer literal check
Dec 21, 2024
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7 changes: 7 additions & 0 deletions clang/lib/Analysis/UnsafeBufferUsage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -463,6 +463,13 @@ AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
return true;
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@rnk rnk Nov 27, 2024

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I think getting the integer constant expr is more general, we can remove the IntegerLiteral test here, and if all tests pass, I would consider it functionally equivalent. This code seems like it was tested to a reasonably high standard.

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@mxms0 mxms0 Dec 21, 2024

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I changed the code and tests still pass, it looks like you're correct. :)

}

// Array index wasn't an integer literal, let's see if it was an enum or
// something similar
const auto IntConst = Node.getIdx()->getIntegerConstantExpr(Finder->getASTContext());
if (IntConst && *IntConst > 0 && *IntConst < size) {
return true;
}

return false;
}

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17 changes: 17 additions & 0 deletions clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,23 @@ void constant_idx_unsafe(unsigned idx) {
buffer[10] = 0; // expected-note{{used in buffer access here}}
}

enum FooEnum {
A = 0,
B = 1,
C = 2,
D
};

void constant_enum_safe() {
int buffer[FooEnum::D] = { 0, 1, 2 };
buffer[C] = 0; // no-warning
}

void constant_enum_unsafe(FooEnum e) {
int buffer[FooEnum::D] = { 0, 1, 2 };
buffer[e] = 0; // expected-warning{{unsafe buffer access}}
}

void constant_id_string(unsigned idx) {
char safe_char = "abc"[1]; // no-warning
safe_char = ""[0];
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