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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - __attribute__((callback(4))) gives confusing error message"
href="https://bugs.llvm.org/show_bug.cgi?id=48107">48107</a>
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<th>Summary</th>
<td>__attribute__((callback(4))) gives confusing error message
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>11.0
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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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
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<th>Component</th>
<td>C
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>felix-llvm@fefe.de
</td>
</tr>
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<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>I am trying to use the callback attribute to annotate functions in my code.
I tried to annotate qmail in my libc header with it. Here is a minimal test
case to illustrate my problem:
typedef int pthread_t;
typedef int pthread_attr_t;
typedef unsigned long size_t;
__attribute__((callback (3, 4)))
int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
void *(*start_routine) (void *), void
*arg);
__attribute__((callback (4)))
void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *,
const void *));
Compiling this gives:
% clang -c y.c
y.c:9:16: error: 'callback' attribute takes no arguments
__attribute__((callback (4)))
^
1 error generated.
Uh, wot? I'm not sure what is happening here. As I understand the
documentation, having just one argument to callback is OK here. But I tried
putting it as (4,1) instead, but that also does not compile, with this error
message:
y.c:9:16: error: 'callback' attribute takes one argument
__attribute__((callback (4, 1)))
What is going on here?</pre>
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