misra/misra-ctu-2-test.c:0:0: information: Bailing out from checking misra/misra-ctu-2-test.c since there was an internal error:
Failed to execute 'python3 /cygdrive/d/a/cppcheck/cppcheck/addons/runaddon.py /cygdrive/d/a/cppcheck/cppcheck/addons/misra.py --cli misra/misra-ctu-2-test.c.1185.dump'.
C:\hostedtoolcache\windows\Python\3.9.13\x64\python.exe: can't open file 'D:\cygdrive\d\a\cppcheck\cppcheck\addons\runaddon.py': [Errno 2] No such file or directory [internalError]

cppcheck/cppcheck in the path looks suspicious. But the path is composed by getFullPath(), which should already check for existence, so dunno.

I think this looks good.

Except on Cygwin. I wonder how this worked before.
We get the exename /cygdrive/d/a/cppcheck/cppcheck/cppcheck, which looks valid, and we also check the existence of the derived paths. Yet Python can't find the scripts.
@chrfranke As our resident Cygwin user, maybe you can take a look?

So apparently we need a relative path in Cygwin for some reason. This is the command line from CI-cygwin.yml:
..\..\cppcheck.exe --dump -DDUMMY --suppress=uninitvar --inline-suppr misra\misra-test.c --std=c89 --platform=unix64

Except on Cygwin. I wonder how this worked before. We get the exename /cygdrive/d/a/cppcheck/cppcheck/cppcheck, which looks valid, and we also check the existence of the derived paths. Yet Python can't find the scripts.

Cygwin emulates Linux as far as possible so readlink("/proc/self/exe", ...) should work on Cygwin. The Cygwin(!) version of python should find the scripts, but any other Windows version never would.

If you want to support both, the following may work because Cygwin programs also understand Windows pathnames:

+#if defined(_WIN32) || defined(__CYGWIN__)
+    success = (GetModuleFileNameA(nullptr, buf, sizeof(buf)) < sizeof(buf));
+#elif defined(__APPLE__)

Thanks for your quick response.

It seems that the Cygwin path (from readlink()) gets translated to a Windows path automatically, but the result is invalid(?):
C:\hostedtoolcache\windows\Python\3.9.13\x64\python.exe: can't open file 'D:\cygdrive\d\a\cppcheck\cppcheck\addons\runaddon.py': [Errno 2] No such file or directory

It usually does not make any sense to pass a Cygwin path containing /cygdrive/ to a non-Cygwin program.
Install Cygwin's version of python (https://cygwin.com/packages/summary/python3.html) and retry.

Someone using the Cygwin version of cppcheck for some reason also wants to use the Cygwin version of python :-)

That did it, thanks again 👍

Can this be merged?

I ran into this as well and when I tried to fix it I came up with the same horrible code we have now because it required the path to be available before we have access to argv[0]. But I deemed that unacceptable so I dumped it.

I didn't even realize that our code already contained the logic partially. If I had I would have just put my code up for review and it would have been fixed earlier.

Sorry about that and thanks for fixing this.

It turns out I didn't delete the code but just didn't finish it: firewave@a997b4e. I haven't checked if there is still something to salvage in there yet.