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I noticed that Visual Studio generates *.ilk files for debug builds and *.iobj files for release builds. As I understand, both of these file types are used as input for incremental linker. What is the difference between them? Can they be used together? How can I disable these files in project settings?

According to this answer, .iobj files are produced to support incremental link-time code generation (aka LTCG, and what used to be called, I believe, 'whole program optimization') and LTCG is normally only enabled for release builds.

One optimisation that LTCG can perform is inline a function from another compilation unit (i.e. source file). The compiler (of course) can't do this. There are no doubt others.

.ilk files, on the other hand, support incremental linking for debug builds, to get fast link times. This is not the same as incremental LTCG, where the linker tries to make use of cross-compilation-unit optimisations that it has done before, again to speed things up, but in a different way.

It follows that to suppress generation of .iobj files, turn off 'incremental link time code generation' for your project, and to suppress generation of .ilk files, turn off 'incremental linking'. I believe that both of these are linker options. But why bother? - they speed up development. Instead, I delete these files when I archive [a version of] my project.

Incremental linking is normally turned off for release builds, although I'm not sure why. Perhaps the two options are mutually incompatible, I've never tried enabling them both at once. Or maybe MS figured that we were fed up with them cluttering up our hard disks with build products, who knows?

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