问题
I migrated a project from Qt4 to Qt5, and it compiles and everything but the application crashes before it even reaches the main function. I know there is a null value that fucks up something at some point, maybe a file that cant find or something, but there are so many .cpps and .h and libraries that its pretty hard to locate the source of the error plus I cant set any breakpoints. I have a lot of debugging data so maybe any of you can guide me in the right direction. I dont know what I would be doing without stack overflow honestly, so thankyou in advance.
When debugging I get different crashes:
The stack in each case shows different crashes, but all of them have something in common, which is this __do_global_ctors thingy, I have researched and apparently it has to do with constructors, but I have no idea what I should be looking for.
if I missed any info please do ask. I hope someone can enlighten me, I am so so close to get this working.
回答1:
The __do_global_ctors() is called before your main(), as the framework needs to instantiate all of the global objects that main() might use.
This method will call the constructors for all static objects, and their component objects. I.e. all static constructors.
From the look of the stack trace, it appears that the segfault occurs during the construction of a QGlobalStatic<QMutex, [incomlpete types - see trace for details]> object, which makes sense. This is being constructed by qRegisterResourceData as part of qInitResources_mimetypes.
Try placing a breakpoint in this function in qrc_mimetypes.cpp (if you have the source) and see where that gets you. Or look at the Qt documentation for mimetypes initialisation and make sure you've specified your application's resources correctly.
回答2:
I managed to solve the issue by thoughtfully re-compiling all the libraries to Qt5 and making sure all the cpps that the program refered were Qt5 too. Also double-checked the linkings. I thought I had done it but apparently I missed one library.
Mind that some libraries need to be migrated and there are others that you can download and compile directly with Qt5. If you are having this same problem make sure that there are no Qt5 versions of that library before migrating them yourself.
来源：https://stackoverflow.com/questions/23693961/do-global-ctors-segfault-somewhere-in-project-cant-locate-it