On Linux, we occasionally see `EMFILE` ("too many open files") errors
especially when installing a large formula like `llvm`. Currently, this
can be reliably reproduced in a Homebrew/brew GitHub codespace (where
`ulimit -n` seems to be 1024 by default) with `brew install geeqie`,
with the following error message:
Error: Too many open files @ rb_sysopen - /home/linuxbrew/.linuxbrew/Cellar/llvm/20.1.8/bin/tblgen-lsp-server
The reason is that each instance of `PatchELF::Patcher` keeps the ELF
file open. We prepend the `ELFShim` module to the `Pathname` class and
cache the patcher as an instance variable, which means that the ELF file
remains open so long as the `Pathname` instance is still alive even if
we don't need to access the ELF metadata anymore. When performing
certain checks (e.g., linkage), we also store these `Pathname`
instances, so the number of open file descriptors simply keeps
increasing.
We can fix that by not caching the patcher and only use it when
necessary. We create a patcher instance whenever we need to read or
write ELF metadata, and reading of metadata is consolidated into the
existing `ELFShim::Metadata` class so that we don't repeatedly create
patcher instances.
A fix for a file descriptor leak issue in patchelf.rb has been submitted
at https://github.com/david942j/patchelf.rb/pull/48. Together with that,
this fixes#19177, #19866, #20223, #20302.
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