Run only top-level recursive lcov

This is the way lcov was intended to be used.  It is much faster and
more robust and makes the makefiles simpler than running it in each
subdirectory.

The previous coding ran gcov before lcov, but that is useless because
lcov/geninfo call gcov internally and use that information.  Moreover,
this led to complications and failures during parallel make.  This
separates the two targets:  You either use "make coverage" to get
textual output from gcov or "make coverage-html" to get an HTML report
via lcov.  (Using both is still problematic because they write the same
output files.)

Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

.gitignore

@@ -23,6 +23,7 @@ objfiles.txt
 *.gcov.out
 lcov.info
 coverage/
+coverage-html-stamp
 *.vcproj
 *.vcxproj
 win32ver.rc

doc/src/sgml/regress.sgml

@@ -706,6 +706,19 @@ make coverage-html
     The <command>make</command> commands also work in subdirectories.
    </para>
 
+   <para>
+    If you don't have <command>lcov</command> or prefer text output over an
+    HTML report, you can also run
+<screen>
+make coverage
+</screen>
+    instead of <literal>make coverage-html</literal>, which will
+    produce <filename>.gcov</filename> output files for each source file
+    relevant to the test.  (<literal>make coverage</literal> and <literal>make
+    coverage-html</literal> will overwrite each other's files, so mixing them
+    might be confusing.)
+   </para>
+
    <para>
     To reset the execution counts between test runs, run:
 <screen>

src/Makefile.global.in

@@ -874,25 +874,29 @@ endif # enable_nls
 
 ifeq ($(enable_coverage), yes)
 
-# There is a strange interaction between lcov and existing .gcov
-# output files.  Hence the rm command and the ordering dependency.
+# make coverage -- text output
 
-gcda_files := $(wildcard *.gcda)
+local_gcda_files = $(wildcard *.gcda)
 
-lcov.info: $(gcda_files)
-	rm -f *.gcov .*.gcov
-	$(if $^,$(LCOV) -d . -c -o $@ $(LCOVFLAGS) --gcov-tool $(GCOV))
+coverage: $(local_gcda_files:.gcda=.c.gcov)
 
-%.c.gcov: %.gcda | lcov.info
+%.c.gcov: %.gcda
 	$(GCOV) -b -f -p -o . $(GCOVFLAGS) $*.c >$*.c.gcov.out
 
-coverage: $(gcda_files:.gcda=.c.gcov) lcov.info
+# make coverage-html -- HTML output via lcov
 
 .PHONY: coverage-html
-coverage-html: coverage
+coverage-html: coverage-html-stamp
+
+coverage-html-stamp: lcov.info
 	rm -rf coverage
-	mkdir coverage
-	$(GENHTML) --show-details --legend --output-directory=coverage --title=PostgreSQL --num-spaces=4 --prefix=$(abs_top_srcdir) `find . -name lcov.info -print`
+	$(GENHTML) --show-details --legend --output-directory=coverage --title=PostgreSQL --num-spaces=4 --prefix=$(abs_top_srcdir) $<
+	touch $@
+
+all_gcda_files = $(shell find . -name '*.gcda' -print)
+
+lcov.info: $(all_gcda_files)
+	$(LCOV) -d . -c -o $@ $(LCOVFLAGS) --gcov-tool $(GCOV)
 
 
 # hook for clean-up
@@ -900,7 +904,7 @@ clean distclean maintainer-clean: clean-coverage
 
 .PHONY: clean-coverage
 clean-coverage:
-	rm -rf coverage
+	rm -rf coverage coverage-html-stamp
 	rm -f *.gcda *.gcno lcov.info *.gcov .*.gcov *.gcov.out