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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - overrestrictive asm goto gotolabels limitations"
href="https://bugs.llvm.org/show_bug.cgi?id=45903">45903</a>
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<th>Summary</th>
<td>overrestrictive asm goto gotolabels limitations
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>10.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jacob@shuf.ro
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>First of all, I apologize if this is the wrong venue for this bug report.
The following does not compile, even though I believe it should:
---------------------------------------------------
cleanup_cb(*p1) {}
foo(int n) {
int cond;
if (({
asm goto("" ::"r"(cond) : : label0);
1;
}))
label0:;
int a[n];
if (({
asm goto("" ::"r"(cond) : : label1);
1;
}))
label1:;
}
main() {}
---------------------------------------------------
jshufro@660:~/asmgoto$ clang-10 main.c
main.c:1:13: warning: type specifier missing, defaults to 'int'
[-Wimplicit-int]
cleanup_cb(*p1) {}
^
main.c:1:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
cleanup_cb(*p1) {}
^
main.c:1:18: warning: non-void function does not return a value [-Wreturn-type]
cleanup_cb(*p1) {}
^
main.c:3:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
foo(int n) {
^
main.c:7:9: error: cannot jump from this asm goto statement to one of its
possible targets
asm goto("" ::"r"(cond) : : label0);
^
main.c:18:3: note: possible target of asm goto statement
label1:;
^
main.c:12:7: note: jump bypasses initialization of variable length array
int a[n];
^
main.c:22:1: warning: type specifier missing, defaults to 'int'
[-Wimplicit-int]
main() {}
^
5 warnings and 1 error generated.
---------------------------------------------------
This is C-Reduced to be fairly minimal. Replacing the variable length array
with an __attribute__((cleanup)) variable causes a similar issue. It's worth
noting that the error is noting a possible target of asm goto that isn't listed
in the GoToLabels.</pre>
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</p>
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