Buddy Alloc Versions Save

• Add a parameter to buddy_realloc that allows it to ignore data. Useful for resizing buffers when there is no longer any interest in their content.
• Minor style and repo changes.

External changes:

• buddy_walk callback is now invoked for free slots in addition to allocated ones and has an extra parameter to distinguish between free and allocated.
• buddy_fragmentation return type is now an unsigned char that ranges between 0 and 255 and no float types are used. This way fragmentation can be reported when used in environments that don't support the float type.

Internal changes:

• A static inline two_to_the_power_of helper function that returns size_t is used in place of manual power of two calculations.
• The fast square root algorithm used in the fragmentation formula has been replaced with an integer square root algorithm by Martin Guy, 1985.

Misc:

Two years and nine months have passed since this project started and it has now reached the 1.0.0 milestone. Thanks to all contributors and users for their interest in it.

• Remove FAMs and {0} initializers to facilitate interop with strict C++ compilers
  • Clang generates identical code with FAMs and without FAMs
  • GCC generates almost-identical code
• Make the debug functions non-static so that they can be used by code in other units
• Include stdio.h only when BUDDY_PRINTF is not defined
• Add a macro for C++ name mangling

• The allocator is now easier to use within a linux kernel/module.
  • Conforms to the c90-style variable declarations in functions
  • New defines BUDDY_PRINTF, BUDDY_HEADER and BUDDY_FRAG_OPTIONAL added to allow conditional inclusion of functionality and setting a suitable printf-like function for the debug functions.
• Fixed some issues with explicit alignment init functions
• Fixed UB on invalid free calls

• Additional performance improvements
• Stricter compile-time checks
• Fixed code coverage reporting and got coverage back to 100%.

This is a significant performance update achieved by reducing the number of tree reads during allocation.

Running bench.c using gcc -O2 on v0.7 takes 20 seconds vs 16 seconds on v0.7.1 Running bench.c using clang -O3 on v0.7 takes 16 seconds vs 13 seconds on v0.7.1

• Add buddy_arena_free_size that reports the remaining free space in the arena. Note that this is a sum of all slots and not necessarily continuous memory.
• Support setting alignment as an argument to init and sizeof functions. This way an application can use multiple allocator instances with different alignments. The BUDDY_ALLOC_ALIGN define is still supported. This is a change in the internal structure of the allocator which can impact serialized instances. There's no impact to regular users.
• Always use the optimal fit algorithm, drop support for the left-bias one.
• Drop the BUDDY_ALLOC_SAFETY define, always use safety checks.
• Jump to version v0.7. v0.6 was a botched release that was deleted

• Added support for compiling with MSVC
• Made the library usable from C++

• Made all tests work on both 64-bit and 32-bit platforms
• Added a buddy_fragmentation function that measures and reports fragmentation in the arena
• Added buddy_set_left_bias and buddy_set_optimal_fit functions to configure allocation behavior on demand
• Internal optimizations and better code reuse

• The tests now run on powerpc (32-bit, big-endian), powerpc64 (64-bit, big-endian), aarch64 (64-bit, little-endian) and i686 (32-bit, little-endian)
• Fixed unaligned access, run tests with UBSan
• Fixed an internal highest bit position function on 32-bit for SIZE_MAX
• Fixed two invalid printf invocations in internal debug functions