Merge #19688: build: Add support for llvm-cov

75f9659d7a build: Add missed fuzz.coverage/ directory to .gitignore (Hennadii Stepanov)
8ebc0505e9 build: Add missed fuzz_filtered.info to COVERAGE_INFO (Hennadii Stepanov)
c71bdf93d7 build, test: Add support for llvm-cov (Hennadii Stepanov)

Pull request description:

  With this PR it is possible to use `lcov` with clang:
  ```
  $ ./autogen.sh
  $ ./configure --enable-lcov --enable-fuzz --with-sanitizers=fuzzer CC=clang CXX=clang++
  $ make
  $ make cov_fuzz
  ```

  ---

  NOTE: Unfortunately, on my system (`clang version 10.0.0-4ubuntu1`) due to unknown for me reasons `make cov` never finishes, trying to `Processing src/test/test_bitcoin-util_tests.gcda` forever (stopped waiting).

  Closes #12602

ACKs for top commit:
  Crypt-iQ:
    Tested ACK 75f9659d7a
  vasild:
    ACK 75f9659d7

Tree-SHA512: 4bc31b38fa62d70c21f890f17f0340e64d0509cea3c29ff6ac101e90ae65d2032640abf100a380c31557bea4c3f54301c2acc2b88a00cbc5261d54c01358ce4e

.gitignore

@@ -119,7 +119,9 @@ releases
 /*.info
 test_bitcoin.coverage/
 total.coverage/
+fuzz.coverage/
 coverage_percent.txt
+/cov_tool_wrapper.sh
 
 #build tests
 linux-coverage-build

Makefile.am

@@ -65,10 +65,10 @@ OSX_PACKAGING = $(OSX_DEPLOY_SCRIPT) $(OSX_FANCY_PLIST) $(OSX_INSTALLER_ICONS) \
   $(top_srcdir)/contrib/macdeploy/detached-sig-apply.sh \
   $(top_srcdir)/contrib/macdeploy/detached-sig-create.sh
 
-COVERAGE_INFO = baseline.info \
+COVERAGE_INFO = $(COV_TOOL_WRAPPER) baseline.info \
   test_bitcoin_filtered.info total_coverage.info \
   baseline_filtered.info functional_test.info functional_test_filtered.info \
-  test_bitcoin_coverage.info test_bitcoin.info fuzz.info fuzz_coverage.info
+  test_bitcoin_coverage.info test_bitcoin.info fuzz.info fuzz_filtered.info fuzz_coverage.info
 
 dist-hook:
 	-$(GIT) archive --format=tar HEAD -- src/clientversion.cpp | $(AMTAR) -C $(top_distdir) -xf -
@@ -192,7 +192,11 @@ LCOV_FILTER_PATTERN = \
 	-p "src/secp256k1" \
 	-p "depends"
 
-baseline.info:
+$(COV_TOOL_WRAPPER):
+	@echo 'exec $(COV_TOOL) "$$@"' > $(COV_TOOL_WRAPPER)
+	@chmod +x $(COV_TOOL_WRAPPER)
+
+baseline.info: $(COV_TOOL_WRAPPER)
 	$(LCOV) -c -i -d $(abs_builddir)/src -o $@
 
 baseline_filtered.info: baseline.info

configure.ac

@@ -105,6 +105,7 @@ AC_PATH_TOOL(AR, ar)
 AC_PATH_TOOL(RANLIB, ranlib)
 AC_PATH_TOOL(STRIP, strip)
 AC_PATH_TOOL(GCOV, gcov)
+AC_PATH_TOOL(LLVM_COV, llvm-cov)
 AC_PATH_PROG(LCOV, lcov)
 dnl Python 3.5 is specified in .python-version and should be used if available, see doc/dependencies.md
 AC_PATH_PROGS([PYTHON], [python3.5 python3.6 python3.7 python3.8 python3 python])
@@ -680,16 +681,37 @@ if test x$use_lcov = xyes; then
   if test x$LCOV = x; then
     AC_MSG_ERROR("lcov testing requested but lcov not found")
   fi
-  if test x$GCOV = x; then
-    AC_MSG_ERROR("lcov testing requested but gcov not found")
-  fi
   if test x$PYTHON = x; then
     AC_MSG_ERROR("lcov testing requested but python not found")
   fi
   if test x$GENHTML = x; then
     AC_MSG_ERROR("lcov testing requested but genhtml not found")
   fi
-  LCOV="$LCOV --gcov-tool=$GCOV"
+
+  AC_MSG_CHECKING([whether compiler is Clang])
+  AC_PREPROC_IFELSE([AC_LANG_SOURCE([[
+      #if defined(__clang__) && defined(__llvm__)
+      // Compiler is Clang
+      #else
+      #  error Compiler is not Clang
+      #endif
+    ]])],[
+      AC_MSG_RESULT([yes])
+      if test x$LLVM_COV = x; then
+        AC_MSG_ERROR([lcov testing requested but llvm-cov not found])
+      fi
+      COV_TOOL="$LLVM_COV gcov"
+    ],[
+      AC_MSG_RESULT([no])
+      if test x$GCOV = x; then
+        AC_MSG_ERROR([lcov testing requested but gcov not found])
+      fi
+      COV_TOOL="$GCOV"
+  ])
+  AC_SUBST(COV_TOOL)
+  AC_SUBST(COV_TOOL_WRAPPER, "cov_tool_wrapper.sh")
+  LCOV="$LCOV --gcov-tool $(pwd)/$COV_TOOL_WRAPPER"
+
   AX_CHECK_LINK_FLAG([[--coverage]], [LDFLAGS="$LDFLAGS --coverage"],
     [AC_MSG_ERROR("lcov testing requested but --coverage linker flag does not work")])
   AX_CHECK_COMPILE_FLAG([--coverage],[CXXFLAGS="$CXXFLAGS --coverage"],