search

jasonwhite / ducible

A tool to make Windows builds reproducible. (UNMAINTAINED)
MIT License
257 stars 24 forks source link

Incremental build fails due to PDB being different #3

Closed jasonwhite closed 8 years ago

jasonwhite commented 8 years ago

When building incrementally, the linker fails with the error LNK1209: program database 'foo.pdb' differs from previous link; relink or rebuild.

This could be caused by a number of reasons, one being that the resulting PDB is simply not valid. The linker may also keep information about the state of the PDB separately (maybe in the .ilk file). This needs to be researched more.

jasonwhite commented 8 years ago

My hunch was right. It turns out that the .ilk file stores the PDB signature and the linker is comparing it with the one in the EXE/DLL/PDB and failing because they don't match. Doing a search and replace fixes the problem. Unfortunately, the Microsoft Linker Database format is not documented anywhere on the internet (that I could find). An effective solution, albeit hacky, is to simply map the .ilk file into memory, search for the old PDB signature, and replace it with the new one.

jasonwhite commented 8 years ago

Patching the .ilk file solves the failure, but incremental linking still does not run. For now, we will just patch the PDB signature in the .ilk file and ignore that incremental linking is broken. Fixing this will likely be a big job as making the output deterministic will be difficult or impossible when linking incrementally. The primary purpose of this tool is to be run on full rebuilds of release builds (where /INCREMENTAL is not specified).

malkia commented 6 years ago

I don't want to open, but just to cofirm - the issue would be only if the PDB gets reused in the compilation, e.g. if I build my things in a "intermediate/" folder, where there are .pdb, .ilk, etc. files, and then I deploy to a "bin/" folder and "ducible" in there - it should work, right?

jasonwhite commented 6 years ago

Yes, it should just work. If not, submit a separate issue and I'll get it fixed.

Edit: By "work" I mean the tool won't fail, but it might not make the output deterministic. If link is run with /INCREMENTAL , the output cannot be made deterministic.