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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Variable is incorrectly marked as "set but not used" when used with the __cleanup__() attribute"
href="https://bugs.llvm.org/show_bug.cgi?id=51865">51865</a>
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<th>Summary</th>
<td>Variable is incorrectly marked as "set but not used" when used with the __cleanup__() attribute
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Frontend
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>frantisek@sumsal.cz
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>Hello,
Yesterday I came across a possible issue in clang-13 when trying to rebuild[0]
the systemd codebase with one of the nightly[1] LLVM builds. After minimizing
the reproducer, the issue stems from a fact that clang incorrectly marks a
variable as "set but not used" if the variable is used only from the
__cleanup__() function:
Reproducer:
#include <stdio.h>
static void my_cleanup(char **test) {
if (test)
printf("my_cleanup: %s\n", *test);
}
int main(void) {
__attribute__((__cleanup__(my_cleanup))) char *x = NULL;
puts("Hello");
x = "test";
puts("World");
return 0;
}
Expected behavior (clang-12):
# clang --version
clang version 12.0.1 (Fedora 12.0.1-1.fc34)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /bin
# clang -Wall -Wextra -Werror -o test test.c
Unexpected behavior (clang-13):
# clang-13 --version
Ubuntu clang version
13.0.0-++20210914062619+f6b09e394a5f-1~exp1~20210914043438.103
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
# clang-13 -Wall -Wextra -Werror -o test test.c
test.c:9:52: error: variable 'x' set but not used
[-Werror,-Wunused-but-set-variable]
__attribute__((__cleanup__(my_cleanup))) char *x = NULL;
^
1 error generated.
[0] <a href="https://github.com/systemd/systemd/pull/20738">https://github.com/systemd/systemd/pull/20738</a>
[1] <a href="https://apt.llvm.org/">https://apt.llvm.org/</a></pre>
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