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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - GNU extension: Support forward declaring function parameters"
href="https://bugs.llvm.org/show_bug.cgi?id=48273">48273</a>
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<th>Summary</th>
<td>GNU extension: Support forward declaring function parameters
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>11.0
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>josephcsible@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Consider this C function:
void transpose(double (*)[*], int);
void transpose(array, size)
int size;
double (*array)[size];
{
for (int i=1; i<size; i++)
{
for (int j=0; j<i; j++)
{
double t = array[i][j];
array[i][j] = array[j][i];
array[j][i] = t;
}
}
}
It uses a K&R function definition, which is deprecated and will probably be
removed in C2x. To my knowledge, there's no standard replacement for that since
the VLA comes before its size, but a GNU extension allows forward declaring
parameters, like this:
void transpose(double (*)[*], int);
void transpose(int size; double (*array)[size], int size)
{
for (int i=1; i<size; i++)
{
for (int j=0; j<i; j++)
{
double t = array[i][j];
array[i][j] = array[j][i];
array[j][i] = t;
}
}
}
Today, GCC will accept that code, but Clang will not. Can support for that GNU
extension be added to Clang as well?</pre>
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