Bug 2000138

Description of problem:

When building documentation with doxygen 1.9.2 the filenames for the directory dependencies generated here:

https://github.com/doxygen/doxygen/blob/8bbce64cdbaa155499fbabedf5343e9e1d34d378/src/dotdirdeps.cpp#L165

are not reproducible. The dirCount() value depends on the order in which the files are scanned, which depends on the std::filesystem::directory_iterator. This order is not deterministic.

https://en.cppreference.com/w/cpp/filesystem/directory_iterator

says: "directory_iterator is a LegacyInputIterator that iterates over the directory_entry elements of a directory (but does not visit the subdirectories). **The iteration order is unspecified**, except that each directory entry is visited only once. The special pathnames dot and dot-dot are skipped."

Since the dirCount() values are not guaranteed to be constant between runs, they can not be used in the generated documentation or in the filenames used to save it, or the result is not-reproducible.

This causes problems when building packages for Fedora, since packages are built for multiple architectures, and the build system (koji) rejects builds where the set of filenames in a non-architecture dependent (noarch) package is different when built on different architectures.

Here is an example: https://koji.fedoraproject.org/koji/taskinfo?taskID=74850762

The build is rejected because:

BuildError: The following noarch package built differently on different architectures: root-doc-6.24.04-1.fc36.noarch.rpm
rpmdiff output was:
removed     /usr/share/doc/root/html/dir_000586_000029.html
removed     /usr/share/doc/root/html/dir_000586_000034.html
removed     /usr/share/doc/root/html/dir_000586_000043.html
removed     /usr/share/doc/root/html/dir_000586_000056.html
removed     /usr/share/doc/root/html/dir_000586_000063.html
removed     /usr/share/doc/root/html/dir_000586_000066.html
removed     /usr/share/doc/root/html/dir_000586_000075.html
removed     /usr/share/doc/root/html/dir_000586_000344.html
added       /usr/share/doc/root/html/dir_000587_000029.html
added       /usr/share/doc/root/html/dir_000587_000034.html
added       /usr/share/doc/root/html/dir_000587_000043.html
added       /usr/share/doc/root/html/dir_000587_000056.html
added       /usr/share/doc/root/html/dir_000587_000063.html
added       /usr/share/doc/root/html/dir_000587_000066.html
added       /usr/share/doc/root/html/dir_000587_000075.html
added       /usr/share/doc/root/html/dir_000587_000344.html

Version-Release number of selected component (if applicable):

doxygen-1.9.2-1.fc36

How reproducible:

Randomly. But more common with large packages. s390x seems to be more likely to generate files with different filenames than the other architectures.

Steps to Reproduce:
1. Build a package what builds documentation using doxygen.
2. Does not happen always. More likely with large packages with many directories in the source tree.

Actual results:

non-reproducible builds depending on the undefined order of the directory scan.

Expected results:

Reproducible builds not depending on the undefined order of the directory scan.