Building Qt on 64bit Windows: "conversion from 'size_t' to 'int', possible loss of data"

jim_kaiser

Hi there,

I have compiled Qt on Windows XP x64, and use it in my project without these crashes you mention. The size_t to int warning is quite common and mostly harmless. Maybe you could trace the reason of the crash?

jim_kaiser

I forgot to add, we use Visual Studio 2005, with the QMAKESPEC "win32-msvc2005" (The same is used for 64 bit too). Maybe you could try giving the appropriate makespec argument to configure, since you use Visual Studio 2010.

hcwdjk

Well, it's either the way I build Qt, or the way I build my library on Windows, because it works like a charm on 64bit linux.

I tried debugging it in visual studio, but I couldn't figure out how to set it up to break on a crash. I can't even tell what type of crash it is exactly... When I'm debugging on linux using QtCreator it just stops when there's a segfault or other type of crash. VS on the other hand does nothing and lets the app die. How can I set VS to stop the execution on a crash?

bq. Maybe you could try giving the appropriate makespec argument to configure, since you use Visual Studio 2010.

configure.exe properly deafulted to win32-msvc2010, so there's no problem here.

koahnig

As jim_kaiser stated already the warnings are frequently and typically harmless, but you should have made the same experience on linux anyhow.

Maybe you try it without the -fast and -release switches in your configure command.

hcwdjk

bq. the warnings are frequently and typically harmless

Yeah, I didn't really think this through. I must have somehow associated size_t with pointers and thought there are pointers being butchered because some part of the buildsystem thinks it's compiling for x86. That was the best lead I had anyway

bq. but you should have made the same experience on linux anyhow.

Well, I just did a build on 64bit linux and there are no such warnings here.

bq. Maybe you try it without the -fast and -release switches in your configure command.

I'll try it tomorrow and report on the results.

jim_kaiser

bq. VS on the other hand does nothing and lets the app die. How can I set VS to stop the execution on a crash?

Generally, that shouldn't happen. Unless, you're building in release mode, it should break after a crash. You're saying you get no message at all? What about the execution output in Visual Studio, anything useful there? Also, I hope the command prompt is of x64 and not win64, you could explicitly set the environment by calling the appropriate .bat file (something like vcvars_x64.bat) or run vcvarsall.bat with the x64 argument.

koahnig

I have to admit that I did not pay a lot of attention to warnings last time I had built it on linux. As long as it does not stop with an error, it seems to be fine ;-)

hcwdjk

bq. As long as it does not stop with an error, it seems to be fine ;-)

That's a good rule of thumb, but here I was extra wary because I didn't really know what I was doing ;)

hcwdjk

Allright, it seems I'm an idiot after all. I was so sure, that I was doing something wrong with building Qt, I didn't bother to check the one tiny part of code (just 3 lines) I changed when switching to Windows, which caused a bug I had in the code from the beginning to surface. So, sorry for all the fuss ;)

koahnig

Sh.. happens. Good to know that you managed to get it solved.