Re: [PATCH 1/2] perf build: conditionally add feature check flags for libtrace{event,fs}

[Guilherme Amadio <amadio@gentoo.org>]

Hi Arnaldo,

On Thu, Jun 27, 2024 at 05:06:05PM +0200, Guilherme Amadio wrote:
> This avoids reported warnings when the packages are not installed.
> 
> Fixes: 0f0e1f44569061e3dc590cd0b8cb74d8fd53706b
> Signed-off-by: Guilherme Amadio <amadio@gentoo.org>
> ---
>  tools/perf/Makefile.config | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 81f73f68d256..987b48f242d3 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -182,14 +182,6 @@ endif
>  FEATURE_CHECK_CFLAGS-libzstd := $(LIBZSTD_CFLAGS)
>  FEATURE_CHECK_LDFLAGS-libzstd := $(LIBZSTD_LDFLAGS)
>  
> -# for linking with debug library, run like:
> -# make DEBUG=1 PKG_CONFIG_PATH=/opt/libtraceevent/(lib|lib64)/pkgconfig
> -FEATURE_CHECK_CFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --cflags libtraceevent)
> -FEATURE_CHECK_LDFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --libs libtraceevent)
> -
> -FEATURE_CHECK_CFLAGS-libtracefs := $(shell $(PKG_CONFIG) --cflags libtracefs)
> -FEATURE_CHECK_LDFLAGS-libtracefs := $(shell $(PKG_CONFIG) --libs libtracefs)
> -
>  FEATURE_CHECK_CFLAGS-bpf = -I. -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(SRCARCH)/include/uapi -I$(srctree)/tools/include/uapi
>  # include ARCH specific config
>  -include $(src-perf)/arch/$(SRCARCH)/Makefile
> @@ -211,6 +203,17 @@ endif
>  ifneq ($(NO_LIBTRACEEVENT),1)
>    ifeq ($(call get-executable,$(PKG_CONFIG)),)
>    dummy := $(error Error: $(PKG_CONFIG) needed by libtraceevent is missing on this system, please install it)
> +  else
> +    ifeq ($(shell $(PKG_CONFIG) --exists libtraceevent),0)

There is a problem here which I noticed while working on the fix for
the problem reported by Thorsten (in tools/verification/rv). We need

-    ifeq ($(shell $(PKG_CONFIG) --exists libtraceevent),0)
+    ifeq ($(shell $(PKG_CONFIG) --exists libtraceevent 2>&1 1>/dev/null; echo $$?),0)

to produce a 0 in the output, otherwise it doesn't work. I will send a v2 fixing this.

For the feature checks that depend on using FEATURE_CHECK_* like the ones below,
it looks like the best would be to find a good common place to do it instead of
redeclaring these required flags on various subdirectories. I thought about
doing that in tools/build/Makefile.feature, but since these flags depend on
using $(PKG_CONFIG), and that is also set in various places, I thought I'd ask
first before going ahead. The idea I have is to gather somewhere the packages
that are used via their .pc files, and set the appropriate FEATURE_CHECK_* flags
such that all subdirectories could get them automatically. That may require setting 
PKG_CONFIG in a common place as well, and then dropping it from places such as
tools/perf/Makefile.perf. Maybe something like this is Makefile.feature:

PKG_CONFIG = $(CROSS_COMPILE)pkg-config

ifneq ($(call get-executable,$(PKG_CONFIG)),)
    # libtraceevent
    ifeq ($(shell $(PKG_CONFIG) --exists libtraceevent 2>&1 1>/dev/null; echo $$?),0)
      FEATURE_CHECK_CFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --cflags libtraceevent 2>/dev/null)
      FEATURE_CHECK_LDFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --libs libtraceevent 2>/dev/null)
    endif

    # libtracefs
    ifeq ($(shell $(PKG_CONFIG) --exists libtracefs 2>&1 1>/dev/null; echo $$?),0)
      FEATURE_CHECK_CFLAGS-libtracefs := $(shell $(PKG_CONFIG) --cflags libtracefs)
      FEATURE_CHECK_LDFLAGS-libtracefs := $(shell $(PKG_CONFIG) --libs libtracefs)
    endif

    # ... other packages
endif

and this shows that we could also define a function for this, and call it for
each package, which would simplify things a bit more. These are the Makefiles
that need to be adjusted:

tools/perf/Makefile.config
tools/tracing/latency/Makefile.config
tools/tracing/rtla/Makefile.config
tools/verification/rv/Makefile.config

Best regards,
-Guilherme

> +      # for linking with debug library, run like:
> +      # make DEBUG=1 PKG_CONFIG_PATH=/opt/libtraceevent/(lib|lib64)/pkgconfig
> +      FEATURE_CHECK_CFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --cflags libtraceevent)
> +      FEATURE_CHECK_LDFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --libs libtraceevent)
> +    endif
> +    ifeq ($(shell $(PKG_CONFIG) --exists libtracefs),0)
> +      FEATURE_CHECK_CFLAGS-libtracefs := $(shell $(PKG_CONFIG) --cflags libtracefs)
> +      FEATURE_CHECK_LDFLAGS-libtracefs := $(shell $(PKG_CONFIG) --libs libtracefs)
> +    endif
>    endif
>  endif
>  
> -- 
> 2.45.2
>