https://bugs.llvm.org/show_bug.cgi?id=48273
Bug ID: 48273
Summary: GNU extension: Support forward declaring function
parameters
Product: clang
Version: 11.0
Hardware: Other
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: josephcsi...@gmail.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org,
neeil...@live.com, richard-l...@metafoo.co.uk
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?
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