Currently, our memory allocators are being redirected to the correct implementation at compile time by simply using macros. In order to make them swappable at runtime, this commit reshuffles that by instead making use of a global "git_allocator" structure, whose pointers are set up to reference the allocator functions. Like this, it becomes easy to swap out allocators by simply setting these function pointers. In order to initialize a "git_allocator", our provided allocators "stdalloc" and "crtdbg" both provide an init function. This is being called to initialize a passed in allocator struct and set up its members correctly. No support is yet included to enable users of libgit2 to switch out the memory allocator at a global level.
Currently, the `git__free` function is being defined in a single place, only, disregarding whether we use our standard allocators or the crtdbg allocators. This makes it a bit harder to convert our code base to use pluggable allocators, and furthermore makes the border between our two allocators a bit more blurry. Implement a separate `git__crtdbg__free` function for the crtdbg allocator in order to completely separate both allocator implementations.
The crtdbg allocators are currently being implemented as inline functions as part of the "w32_crtdbg_stacktrace.h" header. As we are moving towards pluggable allocators with the help of function pointers, though, we cannot make use of inlining anymore. Instead, we can only have a single implementation of these allocating functions. Move all implementations of the crtdbg allocators into "w32_crtdbg_stacktrace.c".
use consistent names for the #include / #define header guard pattern.
This function has previously been implemented in Windows-specific path handling code as `path__is_dirsep`. As we will need this functionality in other parts, extract the logic into "path.h" alongside with a non-Windows implementation.
This function has previously been implemented in Windows-specific path handling code as `path__is_absolute`. As we will need this functionality in other parts, extract the logic into "path.h" alongside with a non-Windows implementation.
Include fixups
When using the `do_with_retries` macro for retrying filesystem operations in the posix emulation layer, allow the remediation function to return `GIT_RETRY`, meaning that the error was believed to be remediated, and the operation should be retried immediately, without a sleep. This is a slightly more general solution to the problem fixed in #4312.
Fixed an issue where the retry logic on p_unlink sleeps before it tries setting a file to write mode causing unnecessary slowdown.
Next to including several files, our "common.h" header also declares various macros which are then used throughout the project. As such, we have to make sure to always include this file first in all implementation files. Otherwise, we might encounter problems or even silent behavioural differences due to macros or defines not being defined as they should be. So in fact, our header and implementation files should make sure to always include "common.h" first. This commit does so by establishing a common include pattern. Header files inside of "src" will now always include "common.h" as its first other file, separated by a newline from all the other includes to make it stand out as special. There are two cases for the implementation files. If they do have a matching header file, they will always include this one first, leading to "common.h" being transitively included as first file. If they do not have a matching header file, they instead include "common.h" as first file themselves. This fixes the outlined problems and will become our standard practice for header and source files inside of the "src/" from now on.