Referring to this message
https://debbugs.gnu.org/52376#86 it is advised
to keep the .pdmp file in the libexecdir instead of putting it along
side the Emacs executable.
Currently the load_pdump from emacs.c first looks for a .pdmp file in
the same directory where Emacs executable is present. While doing that
it calls load_pdump_find_executable, which tries to resolve symlinks and
finds the real name of the binary being invoked. Then this name is used
to find the .pdmp file.
/* If the executable name contains a slash, we have some kind of
path already, so just resolve symlinks and return the result. */
/* People put on PATH a symlink to the real Emacs
executable, with all the auxiliary files where the real
executable lives. Support that. */
IIUC when searching for the .pdmp file in the libexecdir (path_exec), it
uses argv0 and does not find the actual binary name by resolving
symlinks.
/* Finally, look for basename(argv0)+".pdmp" in PATH_EXEC.
This way, they can rename both the executable and its pdump
file in PATH_EXEC, and have several Emacs configurations in
the same versioned libexec subdirectory. */
Why do you want that?
As the comment from load_pdump_find_executable explains, there are
setups where the /usr/bin/emacs is a symlink managed by something like
alternatives. This symlink eventually points to an Emacs binary like
emacs-28.0.90. These kind of setups are used to have installation of
multiple versions of Emacs on the same system.
Supporting resolution of these symlinks while searching for a .pdmp file
will make it possible to put the .pdmp files in libexecdir instead of
putting those in the /usr/bin/. I think this should be in addition to
the possibilities tried currently.
> Why don't you configure each Emacs build with a different libexecdir
> instead?
Sure, but there are some common files in that directory like hexl,
movemail, etc, which package maintainers have put into a common package
like emacs-common.
How to reproduce?
Install Emacs using make install on your system with correct libexecdir
(it is /usr/libexec/ in my case). This will create a symlink
/usr/bin/emacs which points to /usr/bin/emacs-28.0.90.
Now rename the .pdmp file with:
$ sudo mv /usr/libexec/emacs/28.0.90/x86_64-linux-gnu/{emacs.pdmp,emacs-28.0.90.pdmp}
Now start Emacs:
$ emacs -Q
Loading loadup.el (source)...
Dump mode: nil
Using load-path (/usr/share/emacs/28.0.90/lisp /usr/share/emacs/28.0.90/lisp/emacs-lisp /usr/share/emacs/28.0.90/lisp/progmodes /usr/share/emacs/28.0.90/lisp/language /usr/share/emacs/28.0.90/lisp/international /usr/share/emacs/28.0.90/lisp/textmodes /usr/share/emacs/28.0.90/lisp/vc)
Loading emacs-lisp/byte-run...
Symbol's function definition is void: file-name-sans-extension
Note that the Emacs build above is created with
--with-native-compilation.
I'm not sure if this bug's severity is wishlist or not, so I'm not setting
it right now.