add code coverage option to the build system

configure now has a "--enable-code-coverage" option, and if the
lcov/gcov tools are available a code coverage report can be built with
"make check-code-coverage".

this is mostly based on the AX_CODE_COVERAGE / GNOME_CODE_COVERAGE
macro:

    http://savannah.gnu.org/patch/?8451

but i also looked at knot-dns's code coverage implementation:

    https://github.com/CZNIC-Labs/knot/blob/master/m4/code-coverage.m4

and kevin lyda's pull request:

    https://github.com/protobuf-c/protobuf-c/pull/131/files

.gitignore

 *~
 .*swp
 *.la
+*.gcda
+*.gcno
 *.lo
 *.log
 *.o
@@ -18,6 +20,8 @@
 /configure
 /doxygen-doc
 /libtool
+/protobuf-c-*-coverage.info
+/protobuf-c-*-coverage/
 /stamp-h1
 /test-suite.log
 TAGS

Makefile.am

@@ -22,6 +22,14 @@ AM_CPPFLAGS = \
 AM_CFLAGS = ${my_CFLAGS}
 AM_LDFLAGS =
 
+# code coverage
+
+AM_CFLAGS += ${CODE_COVERAGE_CFLAGS}
+AM_LDFLAGS += ${CODE_COVERAGE_LDFLAGS}
+CODE_COVERAGE_LCOV_OPTIONS = --no-external
+CODE_COVERAGE_IGNORE_PATTERN = "$(abs_top_builddir)/t/*"
+@CODE_COVERAGE_RULES@
+
 #
 # libprotobuf-c
 #

TODO

@@ -19,7 +19,6 @@
   - message unpack alloc failures when allocating unknown field buffers
   - packed message corruption.
     - meta-todo: get a list of all the unpack errors together to check off
-- run gcov
 
 ---------------------
 --- DOCUMENTATION ---

configure.ac

@@ -63,6 +63,8 @@ gl_LD_VERSION_SCRIPT
 
 gl_VALGRIND_TESTS
 
+MY_CODE_COVERAGE
+
 AC_C_BIGENDIAN
 
 AC_OUTPUT

m4/code_coverage.m4

+# SYNOPSIS
+#
+#   MY_CODE_COVERAGE()
+#
+# DESCRIPTION
+#
+#   Defines CODE_COVERAGE_CFLAGS and CODE_COVERAGE_LDFLAGS which should be
+#   included in the CFLAGS and LIBS/LDFLAGS variables of every build target
+#   (program or library) which should be built with code coverage support.
+#   Also defines CODE_COVERAGE_RULES which should be substituted in your
+#   Makefile; and $enable_code_coverage which can be used in subsequent
+#   configure output. CODE_COVERAGE_ENABLED is defined and substituted, and
+#   corresponds to the value of the --enable-code-coverage option, which
+#   defaults to being disabled.
+#
+#   Usage example:
+#   configure.ac:
+#      MY_CODE_COVERAGE
+#
+#   Makefile.am:
+#      @CODE_COVERAGE_RULES@
+#      my_program_LIBS = … $(CODE_COVERAGE_LDFLAGS) …
+#      my_program_CFLAGS = … $(CODE_COVERAGE_CFLAGS) …
+#
+#   This results in a “check-code-coverage” rule being added to any Makefile.am
+#   which includes “@CODE_COVERAGE_RULES@” (assuming the module has been
+#   configured with --enable-code-coverage). Running `make check-code-coverage`
+#   in that directory will run the module’s test suite (`make check`) and build
+#   a code coverage report detailing the code which was touched, then print the
+#   URI for the report.
+#
+# LICENSE
+#
+#   Copyright © 2012, 2014 Philip Withnall
+#   Copyright © 2012 Xan Lopez
+#   Copyright © 2012 Christian Persch
+#   Copyright © 2012 Paolo Borelli
+#   Copyright © 2012 Dan Winship
+#
+#   Derived from Makefile.decl in GLib, originally licenced under LGPLv2.1+.
+#   This file is licenced under LGPLv2.1+.
+
+AC_DEFUN([MY_CODE_COVERAGE],[
+	dnl Check for --enable-code-coverage
+	AC_MSG_CHECKING([whether to build with code coverage support])
+	AC_ARG_ENABLE([code-coverage], AS_HELP_STRING([--enable-code-coverage], [Whether to enable code coverage support]),, enable_code_coverage=no)
+	AM_CONDITIONAL([CODE_COVERAGE_ENABLED], [test x$enable_code_coverage = xyes])
+	AC_SUBST([CODE_COVERAGE_ENABLED], [$enable_code_coverage])
+	AC_MSG_RESULT($enable_code_coverage)
+
+	AS_IF([ test "$enable_code_coverage" = "yes" ], [
+		dnl Check if gcc is being used
+		AS_IF([ test "$GCC" = "no" ], [
+			AC_MSG_ERROR([not compiling with gcc, which is required for gcov code coverage])
+		])
+
+		AC_CHECK_PROG([LCOV], [lcov], [lcov])
+		AC_CHECK_PROG([GENHTML], [genhtml], [genhtml])
+
+		AS_IF([ test -z "$LCOV" ], [
+			AC_MSG_ERROR([The lcov program was not found. Please install lcov!])
+		])
+
+		AS_IF([ test -z "$GENHTML" ], [
+			AC_MSG_ERROR([The genhtml program was not found. Please install lcov!])
+		])
+
+		dnl Build the code coverage flags
+		CODE_COVERAGE_CFLAGS="-O0 -g --coverage"
+		CODE_COVERAGE_LDFLAGS="--coverage"
+
+		AC_SUBST([CODE_COVERAGE_CFLAGS])
+		AC_SUBST([CODE_COVERAGE_LDFLAGS])
+
+    dnl Strip optimisation flags
+    changequote({,})
+    CFLAGS=`echo "$CFLAGS" | $SED -e 's/-O[0-9]*//g'`
+    changequote([,])
+	])
+
+CODE_COVERAGE_RULES='
+# Code coverage
+#
+# Optional:
+#  - CODE_COVERAGE_DIRECTORY: Top-level directory for code coverage reporting.
+#    (Default: $(top_builddir))
+#  - CODE_COVERAGE_OUTPUT_FILE: Filename and path for the .info file generated
+#    by lcov for code coverage. (Default:
+#    $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage.info)
+#  - CODE_COVERAGE_OUTPUT_DIRECTORY: Directory for generated code coverage
+#    reports to be created. (Default:
+#    $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage)
+#  - CODE_COVERAGE_LCOV_OPTIONS: Extra options to pass to the lcov instance.
+#    (Default: empty)
+#  - CODE_COVERAGE_GENHTML_OPTIONS: Extra options to pass to the genhtml
+#    instance. (Default: empty)
+#  - CODE_COVERAGE_IGNORE_PATTERN: Extra glob pattern of files to ignore
+#
+# The generated report will be titled using the $(PACKAGE_NAME) and
+# $(PACKAGE_VERSION). In order to add the current git hash to the title,
+# use the git-version-gen script, available online.
+
+# Optional variables
+CODE_COVERAGE_DIRECTORY ?= $(abs_top_builddir)
+CODE_COVERAGE_OUTPUT_FILE ?= $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage.info
+CODE_COVERAGE_OUTPUT_DIRECTORY ?= $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage
+CODE_COVERAGE_LCOV_OPTIONS ?=
+CODE_COVERAGE_GENHTML_OPTIONS ?=
+CODE_COVERAGE_IGNORE_PATTERN ?=
+
+code_coverage_quiet = $(code_coverage_quiet_$(V))
+code_coverage_quiet_ = $(code_coverage_quiet_$(AM_DEFAULT_VERBOSITY))
+code_coverage_quiet_0 = --quiet
+
+# Use recursive makes in order to ignore errors during check
+check-code-coverage:
+ifeq ($(CODE_COVERAGE_ENABLED),yes)
+	-$(MAKE) $(AM_MAKEFLAGS) -k check
+	$(MAKE) $(AM_MAKEFLAGS) code-coverage-capture
+else
+	@echo "Need to reconfigure with --enable-code-coverage"
+endif
+
+# Capture code coverage data
+code-coverage-capture: code-coverage-capture-hook
+ifeq ($(CODE_COVERAGE_ENABLED),yes)
+	$(LCOV) $(code_coverage_quiet) --directory $(CODE_COVERAGE_DIRECTORY) --capture --output-file "$(CODE_COVERAGE_OUTPUT_FILE).tmp" --test-name "$(PACKAGE_NAME)-$(PACKAGE_VERSION)" --no-checksum --compat-libtool $(CODE_COVERAGE_LCOV_OPTIONS)
+	$(LCOV) $(code_coverage_quiet) --directory $(CODE_COVERAGE_DIRECTORY) --remove "$(CODE_COVERAGE_OUTPUT_FILE).tmp" "/tmp/*" $(CODE_COVERAGE_IGNORE_PATTERN) --output-file "$(CODE_COVERAGE_OUTPUT_FILE)"
+	-@rm -f $(CODE_COVERAGE_OUTPUT_FILE).tmp
+	LANG=C $(GENHTML) $(code_coverage_quiet) --prefix $(CODE_COVERAGE_DIRECTORY) --output-directory "$(CODE_COVERAGE_OUTPUT_DIRECTORY)" --title "$(PACKAGE_NAME)-$(PACKAGE_VERSION) Code Coverage" --legend --show-details "$(CODE_COVERAGE_OUTPUT_FILE)" $(CODE_COVERAGE_GENHTML_OPTIONS)
+	@echo "file://$(abs_builddir)/$(CODE_COVERAGE_OUTPUT_DIRECTORY)/index.html"
+else
+	@echo "Need to reconfigure with --enable-code-coverage"
+endif
+
+# Hook rule executed before code-coverage-capture, overridable by the user
+code-coverage-capture-hook:
+
+ifeq ($(CODE_COVERAGE_ENABLED),yes)
+clean: code-coverage-clean
+code-coverage-clean:
+	-$(LCOV) --directory $(CODE_COVERAGE_DIRECTORY) -z
+	-rm -rf $(CODE_COVERAGE_OUTPUT_FILE) $(CODE_COVERAGE_OUTPUT_FILE).tmp $(CODE_COVERAGE_OUTPUT_DIRECTORY)
+	-find . -name "*.gcda" -o -name "*.gcov" -delete
+endif
+
+GITIGNOREFILES ?=
+GITIGNOREFILES += $(CODE_COVERAGE_OUTPUT_FILE) $(CODE_COVERAGE_OUTPUT_DIRECTORY)
+
+DISTCHECK_CONFIGURE_FLAGS ?=
+DISTCHECK_CONFIGURE_FLAGS += --disable-code-coverage
+
+.PHONY: check-code-coverage code-coverage-capture code-coverage-capture-hook code-coverage-clean
+'
+
+	AC_SUBST([CODE_COVERAGE_RULES])
+	m4_ifdef([_AM_SUBST_NOTMAKE], [_AM_SUBST_NOTMAKE([CODE_COVERAGE_RULES])])
+])