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[PATCH] Avoid recompilation of unrelated files
From: |
Bean |
Subject: |
[PATCH] Avoid recompilation of unrelated files |
Date: |
Wed, 27 Jun 2007 02:52:12 +0800 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
A problem of the grub2 make system is that even the smallest change of source
code can trigger a huge recompilation. Try this:
touch commands/cmp.c
make
The ideal situation is that only files related to cmp module is recompiled.
But unfortunately, this is not the case. The problem lies in file dependence.
cmp.mod: pre-cmp.o mod-cmp.o
pre-cmp.o: cmp_mod-commands_cmp.o
cmp_mod-commands_cmp.o: cmp.c
mod-cmp.o: mod-cmp.c
mod-cmp.c: moddep.lst genmodsrc.sh
def-cmp.lst: pre-cmp.o
und-cmp.lst: pre-cmp.o
moddep.lst: def-cmp.lst und-cmp.lst
cmp.c => cmp_mod-commands_cmp.o => pre-cmp.o => def-cmp.lst and und-cmp.lst
=> moddep.lst
When cmp.c changes, moddep.lst changes. But every mod-*.c depends on
moddep.lst, they all need to be recreated. This will lead to a huge
recompilation process.
def-cmp.lst and und-cmp.lst contains the exported symbol and unresolved symbol
of the module. Their content rarely change. So we can update them only when
it's necessary, not every time we recompile the module.
The solution:
Merge these three rules:
pre-cmp.o: cmp_mod-commands_cmp.o
def-cmp.lst: pre-cmp.o
und-cmp.lst: pre-cmp.o
The output of def-cmp.lst is saved as tmp_pre-cmp.lst. When tmp_pre-cmp.lst
and the old pre-cmp.lst is different, move tmp_pre-cmp.lst to pre-cmp.lst,
otherwise, just delete tmp_pre-cmp.lst. und-cmp.lst can be handled in exactly
the same way.
--
Bean
grub2-genmk.diff
Description: Text document
- [PATCH] Avoid recompilation of unrelated files,
Bean <=