Friendlier getting started in the lack of git_libgit2_init #5578
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A function to provide the initialization count of the library; this is subject to race conditions but is useful for a naive determination as to whether the library has been initialized or not.
We require the library to be initialized with git_libgit2_init before it is functional. However, if a user tries to uses the library without doing so - as they might when getting started with the library for the first time - we will likely crash. This commit introduces some guard rails - now instead of having _no_ allocator by default, we'll have an allocator that always fails, and never tries to set an error message (since the thread-local state is set up by git_libgit2_init). We've modified the error retrieval function to (try to) ensure that the library has been initialized before getting the thread-local error message. (Unfortunately, we cannot determine if the thread local storage has actually been configured, this does require initialization by git_libgit2_init. But a naive attempt should be good enough for most cases.)
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We require the library to be initialized with git_libgit2_init before it is functional. However, if a user tries to uses the library without doing so - as they might when getting started with the library for the first time - we will likely crash.
This PR attempts to set up some guard rails to help a user out in this case.
Now, instead of having no allocator by default, we'll have an allocator that always fails, and never tries to set an error message (since the thread-local state is set up by git_libgit2_init). We've modified the error retrieval function to (try to) ensure that the library has been initialized before getting the thread-local error message.
(Unfortunately, we cannot determine if the thread local storage has actually been configured, this does require initialization by git_libgit2_init. But a naive attempt should be good enough for most cases.)
Of course, this pre-supposes that the first program a user builds will actually check the error message. I'm not certain that this is generally true. I actually often write a quick little program and forget to call git_libgit2_init (but do error checking). But I don't think that I'm a very typical user of the library.
It might be valuable to
fprintf(stderr, "hey! call git_libgit2_init!\n")...? But I thought that I'd start with this PR here and iterate.Depends on #5546