--- /dev/null
+In general, merging process should not be very difficult, but we need to
+track various ABI changes and GCC-specific patches carefully. Here is a
+general list of actions required to perform the merge:
+
+- Checkout recent GCC tree.
+- Run merge.sh script from libsanitizer directory.
+- Modify Makefile.am files into asan/tsan/lsan/ubsan/sanitizer_common/interception
+ directories if needed. In particular, you may need to add new source files
+ and remove old ones in source files list, add new flags to {C, CXX}FLAGS if
+ needed and update DEFS with new defined variables.
+- Apply all needed GCC-specific patches to libsanitizer (note that some of
+ them might be already included to upstream).
+- Apply all necessary compiler changes. Be especially careful here, you must
+ not break ABI between compiler and library.
+- Modify configure.ac file if needed (e.g. if you need to add link against new
+ library for sanitizer lilbs).
+- Remove unused (deleted by merge) files from all source and include
+ directories. Be especially careful with headers, because they aren't listed
+ in Makefiles explicitly.
+- Regenerate configure script and all Makefiles by autoreconf. You should use
+ exactly the same autotools version as for other GCC directories (current
+ version is 2.64, https://www.gnu.org/software/automake/faq/autotools-faq.html
+ for details how to install/use it).
+- Run regression testing on at least three platforms (e.g. x86-linux-gnu,
+ x86_64-linux-gnu, aarch64-linux-gnu).
+- Run {A, UB}San bootstrap on at least three platforms.