Hello,
In the librep there are some .el files, and Michal Jaegermann explained in https://bugzilla.redhat.com/show_bug.cgi?id=431250#c23 that the .elc files are not needed (and sometimes harmful). This is not very consistent with the Emacs guidelines. Maybe the guidelines could be amended for this case?
-- Pat
2008/10/17 Patrice Dumas pertusus@free.fr:
Hello,
In the librep there are some .el files, and Michal Jaegermann explained in https://bugzilla.redhat.com/show_bug.cgi?id=431250#c23 that the .elc files are not needed (and sometimes harmful). This is not very consistent with the Emacs guidelines. Maybe the guidelines could be amended for this case?
I think he's wrong. If something doesn't work when byte compiled (.elc), then that's a bug. When loading many lisp files at startup, byte compilation still provides noticeable speedup, even on recent machines. So, no, I'd oppose changing the guidelines in this regard. It's a bit like saying "we don't need .pyc" files, as we can work just from the .py files (except that emacs doesn't do automatic byte compilation in the way that python does if a pyc isn't present or is older than the .py).
Michal does allude to one ugliness of byte compilation - you do often need a packages .el files around when doing byte compilation of another package for function definitions, and this can lead to bootstrapping needs (see emacs-vm and emacs-bbdb for an example).
[As an aside, that package should really be putting its files in a subdirectory of %{emacs_lispdir}.]
On Wednesday 22 October 2008, Jonathan Underwood wrote:
2008/10/17 Patrice Dumas pertusus@free.fr:
Hello,
In the librep there are some .el files, and Michal Jaegermann explained in https://bugzilla.redhat.com/show_bug.cgi?id=431250#c23 that the .elc files are not needed (and sometimes harmful). This is not very consistent with the Emacs guidelines. Maybe the guidelines could be amended for this case?
I think he's wrong. If something doesn't work when byte compiled (.elc), then that's a bug.
Strictly speaking, I don't think it's always quite that black and white.
Depending on the .el, byte compilation in one configuration may end up "optimizing away" things that are not needed in that configuration, but might be needed in other configurations where the .elc is supposed to be used. Or the other way around, it may end up byte compiling things that are needed in the build configuration but are not needed and can cause duplicate definitions or other weirdness in others. For example detecting availability of some features - typically .el that supports multiple *Emacs versions by providing internal replacements for some things not found in the build configuration - and conditionally byte compiling them.
Reviewing eval-when-compile's in the .el might reveal some but not all potential problems. defmacro's are another thing that could be useful to check (AFAIU, IIRC, but then again I don't have that deep knowledge about these things).
In practice this is rarely a problem in Fedora as the .elc are quite likely to be used in pretty much the same configuration (Emacs version, other lisp libs loaded from load-path) as with what they were built with. But if configurations differ enough such as .elc byte compiled with Emacs ending up in XEmacs' load path or vice versa, or .elc byte compiled with one *Emacs version and run with another, breakage is not at all unlikely. Granted, the best fix for these situations is not omitting byte-compilation altogether, but rather ensuring incompatible *emacs don't mess around with .elcs in each others' load paths, and using strict enough rpm level dependency versioning on the target *emacs.
2008/10/23 Ville Skyttä ville.skytta@iki.fi:
On Wednesday 22 October 2008, Jonathan Underwood wrote:
2008/10/17 Patrice Dumas pertusus@free.fr:
Hello,
In the librep there are some .el files, and Michal Jaegermann explained in https://bugzilla.redhat.com/show_bug.cgi?id=431250#c23 that the .elc files are not needed (and sometimes harmful). This is not very consistent with the Emacs guidelines. Maybe the guidelines could be amended for this case?
I think he's wrong. If something doesn't work when byte compiled (.elc), then that's a bug.
Strictly speaking, I don't think it's always quite that black and white.
Depending on the .el, byte compilation in one configuration may end up "optimizing away" things that are not needed in that configuration, but might be needed in other configurations where the .elc is supposed to be used. Or the other way around, it may end up byte compiling things that are needed in the build configuration but are not needed and can cause duplicate definitions or other weirdness in others. For example detecting availability of some features - typically .el that supports multiple *Emacs versions by providing internal replacements for some things not found in the build configuration - and conditionally byte compiling them.
Reviewing eval-when-compile's in the .el might reveal some but not all potential problems. defmacro's are another thing that could be useful to check (AFAIU, IIRC, but then again I don't have that deep knowledge about these things).
In practice this is rarely a problem in Fedora as the .elc are quite likely to be used in pretty much the same configuration (Emacs version, other lisp libs loaded from load-path) as with what they were built with.
Yes, key here is having the correct BuildRequires to ensure other elisp packages of relevance are installed at build time (eg. emacs-vm and emacs-bbdb require each other at build time to ensure the correct macros are compiled).
But if
configurations differ enough such as .elc byte compiled with Emacs ending up in XEmacs' load path or vice versa, or .elc byte compiled with one *Emacs version and run with another, breakage is not at all unlikely. Granted, the best fix for these situations is not omitting byte-compilation altogether, but rather ensuring incompatible *emacs don't mess around with .elcs in each others' load paths, and using strict enough rpm level dependency versioning on the target *emacs.
Agreed, but currently we try to mitigate that by having packages Require the version of Emacs that was used for byte compilation (or a later version) with the rather messy macros in the guidelines. If we want to broaden our scope further to allow for multiple emacs versions to be installed, then we can do what Debian does. But, really, I think that's an unnecessary world of pain.
packaging@lists.fedoraproject.org
-
Jonathan Underwood -
Patrice Dumas -
Ville Skyttä