Junio C Hamano <gitster@xxxxxxxxx> writes: > Phillip Wood <phillip.wood123@xxxxxxxxx> writes: > >> On 22/02/2024 17:50, Calvin Wan wrote: > >>> +libgit.a, which is then linked against by common-main.o with other >>> +external dependencies and turned into the Git executable. >> >> I found this description a bit confusing. As I understand it to build >> git we link git.o against common-main.o, libgit.a, xdiff/lib.a, >> reftable/libreftable.a and libpcre etc. > > In addition, there is no single "the Git executable", simply because > not everything is builtin command. The purpose of using libgit.a is > because we are too lazy to list and maintain all the internal > dependencies to link final executables like 'git' (which has all the > built-in command implementations) and 'git-remote-curl' (which is a > standalone program). Instead of feeding exact list of object files > to "$(CC) -o git" command line, we throw everything into libgit.a > and let the linker pick what is needed. To link "git", we may > include all builtin/*.o, git.o, common-main.o, libgit.a and the > external [*] library dependencies they have. To link "git-daemon", > we may not link builtin/*.o and git.o and link daemon.o instead. > > Side note: here I am counting xdiff/lib.a as an external > library as it is mostly a borrowed code. > > In other words, libgit.a is not a true library in the sense that it > was designed to be _used_ as a library. It was merely a detail of > how we implemented lazy dependency management in our build process, > which happend with 0a02ce72 (Clean up the Makefile a bit., > 2005-04-18) whose commit log message uses air-quotes around the word > "library". Somehow I did not realize that this was going on. Thank you for pointing this out! It does make me wonder if we should stop being lazy and do the work that the linker has been doing for us "for free" ourselves. IOW, stop linking against a monolithic libgit.a. That way we would replace implicit dependencies with explicit ones, which might help us understand which things need what. But maybe doing that is super painful, so, maybe it's not worth it. IDK.
