Re: [Qemu-devel] [PATCH v3 03/18] build-sys: add a rule to print a variable

[Philippe Mathieu-Daudé]

Hi Marc-André,

On 01/04/2018 01:05 PM, Marc-André Lureau wrote:
> $ make print-CFLAGS
> CFLAGS=-fsanitize=address -Og -g

smiley mode:

$ make print-*
*=*

I didn't understood this one:

$ make print-\$
  CC      tests/qemu-iotests/socket_scm_helper.o
  LINK    tests/qemu-iotests/socket_scm_helper
  GEN     qga/qapi-generated/qga-qapi-types.h
  GEN     qga/qapi-generated/qga-qapi-visit.h
  GEN     qga/qapi-generated/qga-qmp-commands.h
  CC      qga/commands.o
  ...


> Trick from various sources:
> https://stackoverflow.com/questions/16467718/how-to-print-out-a-variable-in-makefile
> https://www.cmcrossroads.com/article/printing-value-makefile-variable
> 
> Signed-off-by: Marc-André Lureau <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Tested-by: Philippe Mathieu-Daudé <address@hidden>

> ---
>  Makefile                    |  5 ++++-
>  docs/devel/build-system.txt | 13 +++++++++++++
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 1671db3bdd..f26ef1b1df 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -8,9 +8,12 @@ SRC_PATH=.
>  
>  UNCHECKED_GOALS := %clean TAGS cscope ctags dist \
>      html info pdf txt \
> -    help check-help \
> +    help check-help print-% \
>      docker docker-% vm-test vm-build-%
>  
> +print-%:
> +     @echo '$*=$($*)'
> +
>  # All following code might depend on configuration variables
>  ifneq ($(wildcard config-host.mak),)
>  # Put the all: rule here so that config-host.mak can contain dependencies.
> diff --git a/docs/devel/build-system.txt b/docs/devel/build-system.txt
> index 386ef36ee3..52501f2ad9 100644
> --- a/docs/devel/build-system.txt
> +++ b/docs/devel/build-system.txt
> @@ -510,3 +510,16 @@ default-configs/$TARGET-NAME file as input.
>  This is the entrypoint used when make recurses to build a single system
>  or userspace emulator target. It is merely a symlink back to the
>  Makefile.target in the top level.
> +
> +
> +Useful make targets
> +===================
> +
> +- help
> +
> +  Print a help message for the most common build targets.
> +
> +- print-VAR
> +
> +  Print the value of the variable VAR. Useful for debugging the build
> +  system.
>