* rt.minfo: Avoid calling realloc with size 0
This is not portable, and memcheck complains about this.
* Add C Valgrind API
Add the BSD-licensed C header files which provide the API for
controlling Valgrind from within programs executed under it.
The files are from Valgrind v3.21.0.
* Add some D bindings for the Valgrind C API
We will use these in the GC implementation to tell Valgrind which
memory operations are OK or not.
* Silence Valgrind warnings caused by GC marking
Allow the conservative GC to scan memory, whether it has been
initialized by the application or not.
* Add test suite for Valgrind
* Unify VALGRIND with MEMSTOMP
The two share the same goal: mark memory which should not be accessed
any more.
* Mask "invalid" access to free lists
The GC stores free lists in the cells of the objects on the list.
We would like to allow the GC to work with these lists, but still
raise a warning if application code attempts to access them.
* Distinguish between writable and unwritable invalidation
Freshly allocated memory should be writable but not readable.
Explicitly deallocated or GC-ed memory should be neither readable or
writable.
* Add use-after-free test
* Invalidate freshly-allocated memory
* Integrate VALGRIND with SENTINEL
* Fix reporting of arrays of structs with destructors
* Re-invalidate reused blocks during malloc/calloc
* Add Changelog entry
* .pre-commit-config.yaml: Exempt vendored files
* etc.valgrind.valgrind: Propagate return values of the vbits functions
* etc.valgrind.valgrind: Add documentation for functions
Copy/adapt the documentation in memcheck.h.
* druntime/test/valgrind: Add no_use_after_gc test
* ci/cirrusci.sh: Install Valgrind on Linux
Run the Druntime Valgrind integration tests.
libc6-dbg is needed to allow Valgrind to redirect certain functions.
* etc.valgrind.valgrind: Add @nogc
Although the GC is the primary user, this is not a restriction of
these Valgrind API wrappers.
* druntime/test/valgrind: Fix no_use_after_gc test with -release
Trick the optimizer to pretend we're doing something with the result
of those invalid memory accesses.
