Re: Debugging of native extensions on windows
Rokas Kupstys <[email protected]> Tue, 14 Mar 2023 09:13:08 +0200
| Newsgroups | gmane.comp.python.devel |
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This is a multi-part message in MIME format. --===============2448879490954855584== Content-Type: multipart/alternative; boundary="------------Q3bz73k0G00ZqTqATAPGtRkO" Content-Language: en-US This is a multi-part message in MIME format. --------------Q3bz73k0G00ZqTqATAPGtRkO Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit As Steve suggested i think most friction-less path is to run python interpreter directly while specifying site-packages of virtualenv in PYTHONPATH. I already specify additional paths there anyway, since extensions are built with cmake and i wanted to achieve fast iteration times, being able to use extensions directly built by cmake, without going through installation problem. Still, i think there can be an improvement in this area, and it would likely be quite cheap. The biggest problem is people being unaware what is going on. IsDebuggerPresent()/CheckRemoteDebuggerPresent() could be used for checking debugger presence and when debugging state of main process and child process do not match, launcher could print some link to documentation describing what is going on and how situation could be solved. I am just not sure about any possible race conditions (no idea how fast debuggers attack to child processes). -- Rokas Kupstys On 2023-03-14 08:35, Christopher Barker wrote: > Is it easier to simply run python outside a virtualenv? They are > great, but maybe when debugging an extension module, it's not so hard > to just not use it :-) > > You also might want to give conda environments a try -- they include > Python, so probably won't have the same issue. > > -CHB > > > > On Mon, Mar 13, 2023 at 4:58 PM Steve Dower <[email protected]> > wrote: > > Hi Rokas > > The typical solution (which I myself use frequently) is to enable > your > debugger to attach to child processes automatically. It can make > things > a bit noisier, but it's generally manageable, especially if you've > got > breakpoints set in your own code. > > Another option is to not use the virtual environment, but set > PYTHONPATH > to your environment's Lib\site-packages directory and then run the > base > interpreter directly. Most of the time, this will be identical, > but it > avoids the extra process. > > Unfortunately, for a variety of reasons, we can't get away from the > redirector process as long as virtual environments keep their current > design. As changing the design would be just as disruptive, we've not > done anything yet, nor do we have any plans to change anything. > > Finally, most discussion about Python occurs at > https://discuss.python.org/ these days. You'll likely find more > help and > discussion over there. > > Cheers, > Steve > > On 3/13/2023 3:25 PM, Rokas Kupstys wrote: > > Hello! > > > > I am dropping this mail to bring up an issue which cost me three > good > > evenings of time. Now that i figured it out i believe it is quite a > > serious usability problem. > > > > Gist of the problem: i have some C++ code wrapped with SWIG, so > a native > > extension. As with all software - there was a bug. However, no > matter > > what i did - i could not debug it in a native debugger. I ran > > ".venv/Scripts/python.exe script.py" in a native debugger and > > breakpoints would not be hit, application would crash > eventually. This > > was especially confusing, because exact same setup worked just > fine on > > linux. I eventually stumbled on to process list showing > > ".venv/Scripts/python.exe" having spawned a subprocess... Which > led me > > to "PC/launcher.c" which is what ".venv/Scripts/python.exe" > really is. I > > cant find much information about this behavior in documentation > even > > after the fact. All in all, this was quite confusing. So now > every time > > i want to debug a native extension i have to start a program and > then > > attach a debugger to it, instead of just hitting "Debug" button > in IDE. > > It gets worse if crash happens immediately, which means i have > to resort > > to things like adding a message box somewhere to block execution > and > > give me enough time to attach the debugger. It works in the end, > but > > user experience is really not great. But whats worse - this is > such a > > non-obvious behavior that many more people may trip on it and waste > > their time. Documenting this behavior would be of little help > too, as > > there is no clear path from the issue to the documentation on > the matter... > > > > So there it is. I am sure it is the way it is for a good reason. > > However, this is a very error-prone process which is likely to > waste > > people's time. So maybe this behavior could be reconsidered? Or > maybe > > there is a solution already, which escaped me? > > > > _______________________________________________ > Python-Dev mailing list -- [email protected] > To unsubscribe send an email to [email protected] > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/[email protected]/message/424LIHYHRQWM5VLQF2PAMLKGCNCKSJDF/ > Code of Conduct: http://python.org/psf/codeofconduct/ > > > > -- > Christopher Barker, PhD (Chris) > > Python Language Consulting > - Teaching > - Scientific Software Development > - Desktop GUI and Web Development > - wxPython, numpy, scipy, Cython --------------Q3bz73k0G00ZqTqATAPGtRkO Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <p>As Steve suggested i think most friction-less path is to run python interpreter directly while specifying site-packages of virtualenv in PYTHONPATH. I already specify additional paths there anyway, since extensions are built with cmake and i wanted to achieve fast iteration times, being able to use extensions directly built by cmake, without going through installation problem.</p> <p>Still, i think there can be an improvement in this area, and it would likely be quite cheap. The biggest problem is people being unaware what is going on. IsDebuggerPresent()/CheckRemoteDebuggerPresent() could be used for checking debugger presence and when debugging state of main process and child process do not match, launcher could print some link to documentation describing what is going on and how situation could be solved. I am just not sure about any possible race conditions (no idea how fast debuggers attack to child processes).<br> </p> <pre class="moz-signature" cols="72">-- Rokas Kupstys</pre> <div class="moz-cite-prefix">On 2023-03-14 08:35, Christopher Barker wrote:<br> </div> <blockquote type="cite" cite="mid:CALn7ch-ad-x1i72r4OGOPrHs24cAJPAsUL7+t=0B2hiG0zq7Fw@mail.gmail.com"> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <div dir="ltr">Is it easier to simply run python outside a virtualenv? They are great, but maybe when debugging an extension module, it's not so hard to just not use it :-) <div><br> </div> <div>You also might want to give conda environments a try -- they include Python, so probably won't have the same issue.</div> <div><br> </div> <div>-CHB</div> <div><br> </div> <div><br> </div> </div> <br> <div class="gmail_quote"> <div dir="ltr" class="gmail_attr">On Mon, Mar 13, 2023 at 4:58 PM Steve Dower <<a href="mailto:[email protected]" moz-do-not-send="true" class="moz-txt-link-freetext">[email protected]</a>> wrote:<br> </div> <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Rokas<br> <br> The typical solution (which I myself use frequently) is to enable your <br> debugger to attach to child processes automatically. It can make things <br> a bit noisier, but it's generally manageable, especially if you've got <br> breakpoints set in your own code.<br> <br> Another option is to not use the virtual environment, but set PYTHONPATH <br> to your environment's Lib\site-packages directory and then run the base <br> interpreter directly. Most of the time, this will be identical, but it <br> avoids the extra process.<br> <br> Unfortunately, for a variety of reasons, we can't get away from the <br> redirector process as long as virtual environments keep their current <br> design. As changing the design would be just as disruptive, we've not <br> done anything yet, nor do we have any plans to change anything.<br> <br> Finally, most discussion about Python occurs at <br> <a href="https://discuss.python.org/" rel="noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://discuss.python.org/</a> these days. You'll likely find more help and <br> discussion over there.<br> <br> Cheers,<br> Steve<br> <br> On 3/13/2023 3:25 PM, Rokas Kupstys wrote:<br> > Hello!<br> > <br> > I am dropping this mail to bring up an issue which cost me three good <br> > evenings of time. Now that i figured it out i believe it is quite a <br> > serious usability problem.<br> > <br> > Gist of the problem: i have some C++ code wrapped with SWIG, so a native <br> > extension. As with all software - there was a bug. However, no matter <br> > what i did - i could not debug it in a native debugger. I ran <br> > ".venv/Scripts/python.exe script.py" in a native debugger and <br> > breakpoints would not be hit, application would crash eventually. This <br> > was especially confusing, because exact same setup worked just fine on <br> > linux. I eventually stumbled on to process list showing <br> > ".venv/Scripts/python.exe" having spawned a subprocess... Which led me <br> > to "PC/launcher.c" which is what ".venv/Scripts/python.exe" really is. I <br> > cant find much information about this behavior in documentation even <br> > after the fact. All in all, this was quite confusing. So now every time <br> > i want to debug a native extension i have to start a program and then <br> > attach a debugger to it, instead of just hitting "Debug" button in IDE. <br> > It gets worse if crash happens immediately, which means i have to resort <br> > to things like adding a message box somewhere to block execution and <br> > give me enough time to attach the debugger. It works in the end, but <br> > user experience is really not great. But whats worse - this is such a <br> > non-obvious behavior that many more people may trip on it and waste <br> > their time. Documenting this behavior would be of little help too, as <br> > there is no clear path from the issue to the documentation on the matter...<br> > <br> > So there it is. I am sure it is the way it is for a good reason. <br> > However, this is a very error-prone process which is likely to waste <br> > people's time. So maybe this behavior could be reconsidered? Or maybe <br> > there is a solution already, which escaped me?<br> > <br> <br> _______________________________________________<br> Python-Dev mailing list -- <a href="mailto:[email protected]" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">[email protected]</a><br> To unsubscribe send an email to <a href="mailto:[email protected]" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">[email protected]</a><br> <a href="https://mail.python.org/mailman3/lists/python-dev.python.org/" rel="noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://mail.python.org/mailman3/lists/python-dev.python.org/</a><br> Message archived at <a href="https://mail.python.org/archives/list/[email protected]/message/424LIHYHRQWM5VLQF2PAMLKGCNCKSJDF/" rel="noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://mail.python.org/archives/list/[email protected]/message/424LIHYHRQWM5VLQF2PAMLKGCNCKSJDF/</a><br> Code of Conduct: <a href="http://python.org/psf/codeofconduct/" rel="noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">http://python.org/psf/codeofconduct/</a><br> </blockquote> </div> <br clear="all"> <div><br> </div> <span class="gmail_signature_prefix">-- </span><br> <div dir="ltr" class="gmail_signature"> <div dir="ltr">Christopher Barker, PhD (Chris)<br> <br> Python Language Consulting<br> - Teaching<br> - Scientific Software Development<br> - Desktop GUI and Web Development<br> - wxPython, numpy, scipy, Cython<br> </div> </div> </blockquote> </body> </html> --------------Q3bz73k0G00ZqTqATAPGtRkO-- --===============2448879490954855584== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline