This is not allowed in C++20, and GCC 14 warns about it:
../src/libutil/ref.hh:26:20: warning: template-id not allowed for constructor in C++20 [-Wtemplate-id-cdtor]
26 | explicit ref<T>(const std::shared_ptr<T> & p)
| ^
../src/libutil/ref.hh:26:20: note: remove the '< >'
../src/libutil/ref.hh:33:21: warning: template-id not allowed for constructor in C++20 [-Wtemplate-id-cdtor]
33 | explicit ref<T>(T * p)
| ^
../src/libutil/ref.hh:33:21: note: remove the '< >'
Known behavior changes:
- `MemorySourceAccessor`'s comparison operators no longer forget to
compare the `SourceAccessor` base class.
Progress on #10832
What remains for that issue is hopefully much easier!
Also move `SourcePath` into `libutil`.
These changes allow `error.hh` and `error.cc` to access source path and
position information, which we can use to produce better error messages
(for example, we could consider omitting filenames when two or more
consecutive stack frames originate from the same file).
This fixes a class of crashes and introduces ptr<T> to make the
code robust against this failure mode going forward.
Thanks regnat for the idea of a ref<T> without overhead!
Closes#4895Closes#4893Closes#5127Closes#5113
Caching path info is generally useful. For instance, it speeds up "nix
path-info -rS /run/current-system" (i.e. showing the closure sizes of
all paths in the closure of the current system) from 5.6s to 0.15s.
This also eliminates some APIs like Store::queryDeriver() and
Store::queryReferences().
