Merge branch 'jk/build-with-asan' into next

The build procedure has been improved to allow building and testing
Git with address sanitizer more easily.

* jk/build-with-asan:
  Makefile: disable unaligned loads with UBSan
  Makefile: turn off -fomit-frame-pointer with sanitizers
  Makefile: add helper for compiling with -fsanitize
  test-lib: turn on ASan abort_on_error by default
  test-lib: set ASAN_OPTIONS variable before we run git

Makefile

@@ -1023,6 +1023,14 @@ ifdef DEVELOPER
 CFLAGS += $(DEVELOPER_CFLAGS)
 endif
+ifdef SANITIZE
+BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)
+BASIC_CFLAGS += -fno-omit-frame-pointer
+ifeq ($(SANITIZE),undefined)
+BASIC_CFLAGS += -DNO_UNALIGNED_LOADS
+endif
+endif
+
 ifndef sysconfdir
 ifeq ($(prefix),/usr)
 sysconfdir = /etc

t/test-lib.sh

@@ -36,6 +36,14 @@ then
 fi
 GIT_BUILD_DIR="$TEST_DIRECTORY"/..
+# If we were built with ASAN, it may complain about leaks
+# of program-lifetime variables. Disable it by default to lower
+# the noise level. This needs to happen at the start of the script,
+# before we even do our "did we build git yet" check (since we don't
+# want that one to complain to stderr).
+: ${ASAN_OPTIONS=detect_leaks=0:abort_on_error=1}
+export ASAN_OPTIONS
+
 ################################################################
 # It appears that people try to run tests without building...
 "$GIT_BUILD_DIR/git" >/dev/null
@@ -148,9 +156,6 @@ else
 	}
 fi
-: ${ASAN_OPTIONS=detect_leaks=0}
-export ASAN_OPTIONS
-
 # Protect ourselves from common misconfiguration to export
 # CDPATH into the environment
 unset CDPATH