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Bug #47902 free_op1 warnings
Submitted: 2009-04-05 17:23 UTC Modified: 2009-04-14 01:00 UTC
Avg. Score:1.2 ± 0.6
Reproduced:1 of 2 (50.0%)
Same Version:0 (0.0%)
Same OS:0 (0.0%)
From: pierre dot php at gmail dot com Assigned: dmitry (profile)
Status: No Feedback Package: Compile Warning
PHP Version: 5.3CVS-2009-04-05 (snap) OS:
Private report: No CVE-ID: None
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 [2009-04-05 17:23 UTC] pierre dot php at gmail dot com
zend\zend_vm_execute.h(17488) : warning C4101: 'free_op1' : unreferenced local variable

dozen of times, the generation script could be fixed to silent them.


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 [2009-04-06 11:25 UTC]
These warnings occurs because of inaccurate C compiler behaviour.
In case you look into zend\zend_vm_execute.h(17488) and the whole function, you would see that free_op1 is used in this function, however the code which references the variable is unreachable.

A general solution to eliminate such warnings would require parsing of C source code. I don't think it make sense to invest time into it to just to remove warnings.
 [2009-04-06 11:37 UTC]
It is not that important to fix, you asked me to open a bug about it :)

However, there is no inaccurate behavior, if the code using this variable is unreachable, then the variable is not used at all (typically if (0) will striped out).
 [2009-04-06 13:54 UTC]
Dmitry, I looked at the MSDN for C4101 for example:

struct a {
 static int b() {
  return 1;

int main() {
 A c;
 int d = c.func();

 return d;

The "A c;" line generates a C4101 because b is a static function and therefore no instance is needed to call it, in C++ that would mean main should looks like:

int main() {
 int d = A::func();

 return d;

Its documentation is at:
 [2009-04-14 01:00 UTC] php-bugs at lists dot php dot net
No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".
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