I Test today to launch lonely
xdebug_start_trace(). This runs OK

So the problem seems to come from the file name. The sequences
fopen($file, a+);
fclose($file);
xdebug_start_trace($file, 7)
lead to the error.
Even in this test the file $file exist (with the right name) xdebug_start_trace should overwrite it ( a file with the right name is generated).

I will may be find the solution, but I do think that this error on the file could be reported, because there are many reason not to be able to xdebug_start_trace could fail.

I think that if the problems find a solution here it must be sent to quality to get a better error message.

Could you show me a working script that shows the problem. The last note's code clearly makes no sense. Please include all filenames/directory names as well. And run it with:

strace php yourSmallScript.php 2>/tmp/strace.log

and please attach strace.log to this bug as well.

OK it was shortened. In fact I simply open and close the file to test the validity of the name and the rights before launching xdebug.
As the file
1- is correctly opened and closed
2- when I use the default parameters xdebug_start_trace() the trace runs

The problem comes from xdebug

The full code id a little long because of the check up of xdebug context. So I have not submitted to earn time.

I made the test using a full name of the file (get the realpath of the subdir) and concat with the file name. It runs normally.

Looking at the xdebug error table (with the error case) I found that the name of the file was not right :

the name is "__trac/xd/<name>" the name doesn't matters.

The table contains xdebug_start_trace(" trac/xd/<name>)

So I think that if the relative name begins with chars "_" they are truncated or replaced by blanks. This generates the error.

So a test code should be

$subdir="__trac\xd\";
$file="sample.htm";
$ft=fopen($subdir.$file,'a+');
fclose($ft);
xdebug_start_trace($subdir.$file, 7) ; // This crashes : cannot run...

While

$subdir="__trac\xd\";
$file="sample.htm";
$realpsubdir=realpath($subdir);
$ft=fopen($subdir.$file,'a+');
fclose($ft);
xdebug_start_trace($realpsubdir.$file, 7) ; // Is OK

It seems well that the problem comes from the subdir name.

Is this still a problem with the latest version of xdebug?

Unable to reproduce, and no feedback provided. I'm closing this out, but feel free to reopen if you can provide the requested information.