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C++: Support more "noreturn" attributes in DefaultOptions #18510

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Jan 16, 2025
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C++: Support more "noreturn" attributes in DefaultOptions #18510

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f4f5f28
C++: Add more noreturn attribute tests
jketema Jan 16, 2025
bd40d24
C++: Support more "noreturn" attributes in DefaultOptions
jketema Jan 16, 2025
d027e0c
C++: Add change note
jketema Jan 16, 2025
52eef7c
C++: Fix typo in test
jketema Jan 16, 2025
ff0d495
C++: Fix change note
jketema Jan 16, 2025
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6 changes: 3 additions & 3 deletions cpp/ql/lib/DefaultOptions.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -54,11 +54,11 @@ class Options extends string {
*
* By default, this holds for `exit`, `_exit`, `_Exit`, `abort`,
* `__assert_fail`, `longjmp`, `__builtin_unreachable` and any
* function with a `noreturn` or `__noreturn__` attribute or
* `noreturn` specifier.
* function with a `noreturn`, `__noreturn__`, `_Noreturn`, or
* `_noreturn` attribute or `noreturn` specifier.
*/
predicate exits(Function f) {
f.getAnAttribute().hasName(["noreturn", "__noreturn__"])
f.getAnAttribute().hasName(["noreturn", "__noreturn__", "_Noreturn", "_noreturn"])
or
f.getASpecifier().hasName("noreturn")
or
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4 changes: 4 additions & 0 deletions cpp/ql/lib/change-notes/2025-01-16-noreturn.md
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@@ -0,0 +1,4 @@
---
category: minorAnalysis
---
* `DefaultOptions::exits` now holds for C23 functions with the `_Noreturn` or `__Noreturn__` attribute.
26 changes: 25 additions & 1 deletion cpp/ql/test/query-tests/jsf/4.13 Functions/AV Rule 114/test.c
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@@ -1,4 +1,4 @@
// semmle-extractor-options: -std=c11
// semmle-extractor-options: -std=c23
int f1(void) {
int x = 1;
return 2;
Expand Down Expand Up @@ -110,3 +110,27 @@ int f17() {
if (__builtin_expect(1, 0))
__builtin_unreachable(); // GOOD
}

[[_Noreturn]] void f18();

int f19() {
f18(); // GOOD
}

[[___Noreturn__]] void f20();

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What's going on with __Noreturn__ (in the change note), ___Noreturn__ (here, with the extra _), and the predicate itself (which list neither)?

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It should be with just two _, well spotted. Let me temporarily put this back in draft and fix this.

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I'm wrong. It should be three _ as a prefix and two as a suffix, so it's just the change note that's incorrect. See: https://en.cppreference.com/w/c/language/attributes/noreturn. Note that the lower case version just has two _ both as prefix and as suffix.

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Fixed.

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The predicate itself does not list ___Noreturn__, as the frontend strips off two of the _ in the prefix and also strips off the __ suffix. So, those do not end up in the database.

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Wow, they've made this unnecessarily fiddly!

int f21() {
f20(); // GOOD
}

[[noreturn]] void f22();

int f23() {
f22(); // GOOD
}

[[___noreturn__]] void f24();

int f25() {
f24(); // GOOD
}
7 changes: 7 additions & 0 deletions cpp/ql/test/query-tests/jsf/4.13 Functions/AV Rule 114/test.cpp
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Expand Up @@ -188,3 +188,10 @@ int g22() {
int g23() {
Aborting().a(); // GOOD [FALSE POSITIVE]
}

[[__noreturn__]]
int g24();

int g25() {
g24(); // GOOD
}
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