dmd can no longer read files from a network share: dmd \\network\share\test.d ... Error: module `test` is in file '\\network\share\test.d' which cannot be read You can also no longer pass in file names with the extension long file prefix: dmd \\?\c:\tmp\test.d ... Error: module `test` is in file '\\?\c:\tmp\test.d' which cannot be read Redirecting some output to special devices fails, too: dmd \\?\c:\tmp\test.d -deps nul: ... Error: invalid file name 'nul:' Introduced in dmd 2.078 by adding prefix \\?\ to filenames unconditionally. This can also confuse generic file tracking for dependency generation as used by msbuild.
https://github.com/dlang/dmd/pull/8741
Closing as it has been merged in stable
Commit pushed to master at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/ac9272cd42a3a2c10639217abf98b166f9b12baf fix issue 19266 - Some source files names are no longer accepted only add the \\?\ prefix if the filename is actually long and does not start with \\ already.