Re: [PATCH v5] selftest: size: Add size test for Linux kernel

On 12/03/2014 10:00 AM, Geert Uytterhoeven wrote:

On Wed, Dec 3, 2014 at 5:29 PM, Tim Bird [off-list ref] wrote:

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diff --git a/tools/testing/selftests/size/Makefile b/tools/testing/selftests/size/Makefile
new file mode 100644
index 0000000..47f8e9c
--- /dev/null
+++ b/tools/testing/selftests/size/Makefile

@@ -0,0 +1,15 @@
+#ifndef CC
+    CC = $(CROSS_COMPILE)gcc
+#endif

I think the following is preferable:

  CC := $(CROSS_COMPILE)$(CC)


It allows optionally setting a custom CC, as well as optionally CROSS_COMPILE.

I'm not sure I follow this.

If CC is unset, you get only the CROSS_COMPILE prefix.
If CC is set to e.g. 'gcc', then you get a nicely formatted toolchain string.
But if CC already has the prefix applied, then this will result in
  having it duplicated, which surely won't work correctly.

In the long run, I would hope that a higher level Makefile or environment setting
will be setting the toolchain string appropriately (as well as handling build flags)
which is why I wanted to use an ifndef (which Thomas correctly pointed out is just
wrong).

Actually, after getting this tiny program accepted, my next task was working on a
proper fix for handling cross compilation in a more generic (not case-by-case) way.

CROSS_COMPILE prefix usage looks a bit uncoordinated in the tools directory, but most
tests seem to be favoring $(CROSS_COMPILE)gcc.

 $ cd tools ; mgrep CROSS

[...]

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I agree it's desirable not to hardcode gcc, but we seem to be doing it all over
the place already.

Seems like it's time to start integrating the tests with the regular Kbuild
system, which handles cross-compilation fine...

Where possible, yes.  It would be nice to leverage CROSS_COMPILE and CFLAGS, or
a portion thereof, from the Kbuild system (as well a KBUILD_OUTPUT and friends).
It's on my to-do list, after getting my little C program accepted...
 -- Tim