This will build a coverage report under the current directory in
reports/coverage. At the users option a report can be generated by
directly invoking something like:

  make foo/bar/coverage-report.html

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 Makefile               | 13 +++++++++++++
 docs/devel/testing.rst | 11 ++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index cb4af8bf80..7450e0b7b5 100644
--- a/Makefile
+++ b/Makefile
@@ -988,6 +988,16 @@ docs/interop/qemu-qmp-ref.dvi docs/interop/qemu-qmp-ref.html \
     docs/interop/qemu-qmp-ref.txt docs/interop/qemu-qmp-ref.7: \
 	docs/interop/qemu-qmp-ref.texi docs/interop/qemu-qmp-qapi.texi
 
+# Reports/Analysis
+
+%/coverage-report.html:
+	@mkdir -p $*
+	$(call quiet-command,\
+		gcovr -p --html --html-details -o $@, \
+		"GEN", "coverage-report.html")
+
+.PHONY: coverage-report
+coverage-report: $(CURDIR)/reports/coverage/coverage-report.html
 
 ifdef CONFIG_WIN32
 
@@ -1097,6 +1107,9 @@ endif
 	@echo  'Documentation targets:'
 	@echo  '  html info pdf txt'
 	@echo  '                  - Build documentation in specified format'
+ifdef CONFIG_GCOV
+	@echo  '  coverage-report - Create code coverage report'
+endif
 	@echo  ''
 ifdef CONFIG_WIN32
 	@echo  'Windows targets:'
diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index a3652aea14..9dcdd19260 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -166,9 +166,14 @@ If you want to gather coverage information on a single test the ``make
 clean-coverage`` target can be used to any existing coverage
 information before running a single test.
 
-Reports can be obtained by running ``gcov`` command
-on the output files under ``$build_dir/tests/``, please read the
-``gcov`` documentation for more information.
+You can generate a HTML coverage report by executing ``make
+coverage-report`` which will generate into
+./reports/coverage/coverage-report.html. If you want to generate it
+elsewhere simply execute ``make /foo/bar/baz/coverage-report.html``.
+
+Further analysis can be conducted by running the ``gcov`` command
+directly on the various .gcda output files. Please read the ``gcov``
+documentation for more information.
 
 QEMU iotests
 ============
-- 
2.17.1

Hi Alex,

On 06/20/2018 10:20 AM, Alex Bennée wrote:
> This will build a coverage report under the current directory in
> reports/coverage. At the users option a report can be generated by
> directly invoking something like:
> 
>   make foo/bar/coverage-report.html
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  Makefile               | 13 +++++++++++++
>  docs/devel/testing.rst | 11 ++++++++---
>  2 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index cb4af8bf80..7450e0b7b5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -988,6 +988,16 @@ docs/interop/qemu-qmp-ref.dvi docs/interop/qemu-qmp-ref.html \
>      docs/interop/qemu-qmp-ref.txt docs/interop/qemu-qmp-ref.7: \
>  	docs/interop/qemu-qmp-ref.texi docs/interop/qemu-qmp-qapi.texi
>  
> +# Reports/Analysis
> +
> +%/coverage-report.html:

What about the files in the root directory?

> +	@mkdir -p $*
> +	$(call quiet-command,\
> +		gcovr -p --html --html-details -o $@, \
> +		"GEN", "coverage-report.html")

I think this also needs "-r $(SRC_PATH)" for out-of-tree builds.

From GCOVR(1):

       -r ROOT, --root=ROOT
              Defines the root directory for source files.

> +
> +.PHONY: coverage-report
> +coverage-report: $(CURDIR)/reports/coverage/coverage-report.html
>  
>  ifdef CONFIG_WIN32
>  
> @@ -1097,6 +1107,9 @@ endif
>  	@echo  'Documentation targets:'
>  	@echo  '  html info pdf txt'
>  	@echo  '                  - Build documentation in specified format'
> +ifdef CONFIG_GCOV
> +	@echo  '  coverage-report - Create code coverage report'
> +endif
>  	@echo  ''
>  ifdef CONFIG_WIN32
>  	@echo  'Windows targets:'
> diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
> index a3652aea14..9dcdd19260 100644
> --- a/docs/devel/testing.rst
> +++ b/docs/devel/testing.rst
> @@ -166,9 +166,14 @@ If you want to gather coverage information on a single test the ``make
>  clean-coverage`` target can be used to any existing coverage
>  information before running a single test.
>  
> -Reports can be obtained by running ``gcov`` command
> -on the output files under ``$build_dir/tests/``, please read the
> -``gcov`` documentation for more information.
> +You can generate a HTML coverage report by executing ``make
> +coverage-report`` which will generate into
> +./reports/coverage/coverage-report.html. If you want to generate it
> +elsewhere simply execute ``make /foo/bar/baz/coverage-report.html``.

$ make coverage-report
  GEN     coverage-report.html
/bin/sh: 1: gcovr: not found
make: *** [Makefile:995: reports/coverage/coverage-report.html] Error 127

Can you add a line about this prerequisite? (I don't think it's worth a
check in ./configure).

> +
> +Further analysis can be conducted by running the ``gcov`` command
> +directly on the various .gcda output files. Please read the ``gcov``
> +documentation for more information.
>  
>  QEMU iotests
>  ============
> 

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>