ar MRI scripts with Link time optimization breaks Qt build

As a developer, i want to build a mingw windows cross-compiled Qt version with the same build configuration as i use for my Linux build. I use as much optimized build settings as possible, with at least as possible enabled dependencies. This is the reason why i use the Qt configure -ltcg flag to enable link time optimization.

Using the gcc 7.1.1 and no cross-compilation builds fine. Using the mingw and cross-compilation does break the build, because of missing symbols in pcre2. Details are shown in the attached build log.

Update:

rename ticket "Mingw Link time optimization breaks Qt build" to "ar MRI scripts with link time optimization breaks Qt build"

As explained by Martin Schulze, the problem affects a broader range. Everyone who wants to build Qt with:

• (current) compiler stack producing slim lto objects
• using a make spec where qmake generates mri scripts for ar (e.g. based on QMAKE_LINK_OBJECT_MAX)

We think it should be reevaluated if this ticket is out of scope of the Qt build system. We think that at least the Linux to Windows cross compilation should generate the same ar calls as the native Linux compilation does.