Issue #3430 was about exceeding PATH_MAX because of long hashes in package-ids.

I am running cabal-install built with #3431 and #3954 applied and am running into a similar issue.

This time the problem is because PATH_MAX is exceeded due to lots of nested directories within the "dist-newstyle" directory. The problem happens when the following 2 condition are met:

• The users project directory is "medium" length (such as C:\Users\bitc\stuff\experiments\projects\testing\test-project)
• One of the dependencies has a very long name (such as "data-default-instances-containers")

Here is what happens during cabal new-build:

During the build of the dependency(data-default-instances-containers), suspicious haddock warnings shed light on a very long path:
C:\Users\bitc\stuff\experiments\projects\testing\test-project\dist-newstyle\tmp\data-default-instances-containers-9408\data-default-instances-containers-0.0.1\dist\doc\html\data-default-instances-containers

and the dependency finally fails with:

ghc-pkg.exe: dist\package.conf.inplace\:
openBinaryTempFileWithDefaultPermissions: does not exist (No such file or
directory)

The above error is a sign of a PATH_MAX problem.

In my situation, all of the other dependencies built ok. But the length of the string "data-default-instances-containers" is the longest of all of the dependencies, and apparently is just above the threshold that causes it to fail to build. When I move my project directory down a few levels in the filesystem (making it shorter), everything builds fine.

Recommendation: Dependencies should not be built inside "dist-newstyle/tmp" but rather in some temporary directory completely outside of the project dir, probably in some system tmp dir (which can hopefully be assumed to be quite short)