Problem: no code coverage integration

Solution: import ax_code_coverage.m4 from autoconf-archive and use it
in configure.ac and Makefile.am in order to provide a make
check-code-coverage target behind a --enable-code-coverage configure
flag, that can be used to generate a gcov/lcov code coverage report.
Depends on having gcov and lcov installed.

Makefile.am

@@ -273,9 +273,10 @@ endif
 endif
 endif
 
-src_libzmq_la_CPPFLAGS =
-src_libzmq_la_CXXFLAGS = @LIBZMQ_EXTRA_CXXFLAGS@
-src_libzmq_la_LIBADD =
+src_libzmq_la_CPPFLAGS = $(CODE_COVERAGE_CPPFLAGS)
+src_libzmq_la_CFLAGS = $(CODE_COVERAGE_CFLAGS)
+src_libzmq_la_CXXFLAGS = @LIBZMQ_EXTRA_CXXFLAGS@ $(CODE_COVERAGE_CXXFLAGS)
+src_libzmq_la_LIBADD = $(CODE_COVERAGE_LDFLAGS)
 
 if USE_LIBSODIUM
 src_libzmq_la_CPPFLAGS += ${sodium_CFLAGS}
@@ -760,6 +761,8 @@ MAINTAINERCLEANFILES = \
 	$(srcdir)/configure \
 	`find "$(srcdir)" -type f -name Makefile.in -print`
 
+@CODE_COVERAGE_RULES@
+
 dist-hook:
 	-rm $(distdir)/src/platform.hpp
 	@if test -d "$(srcdir)/.git"; \

configure.ac

@@ -16,6 +16,7 @@ AM_INIT_AUTOMAKE(foreign subdir-objects tar-ustar dist-zip)
 m4_pattern_allow([AC_PROG_CC_C99])
 m4_include([m4/ax_check_compile_flag.m4])
 m4_include([m4/ax_cxx_compile_stdcxx_11.m4])
+m4_include([m4/ax_code_coverage.m4])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
 # This lets us use PACKAGE_VERSION in Makefiles
@@ -50,6 +51,7 @@ AC_PROG_CC
 AX_CHECK_COMPILE_FLAG([-std=gnu11], [CFLAGS+=" -std=gnu11"], [AC_PROG_CC_C99])
 AC_PROG_CXX
 AX_CXX_COMPILE_STDCXX_11([ext], [optional])
+AX_CODE_COVERAGE
 AM_PROG_CC_C_O
 AC_PROG_SED
 AC_PROG_AWK