Re: [Xen-devel] [PATCH v2] tools: detect appropriate debug optimization level

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Doug Goldstein writes ("[PATCH v2] tools: detect appropriate debug optimization 
level"):
> When building debug use -Og as the optimization level if its available,
> otherwise retain the use of -O0. -Og has been added by GCC to enable all
> optimizations that to not affect debugging while retaining full
> debugability.
...
> -CFLAGS += -O0 -g3
> +CFLAGS += $(call cc-option,$(CC),-Og,-O0)
> +CFLAGS += -g3

I think CFLAGS is a variable which is expanded late, at each reference
site - a `recursively expanded' variable.

The result is that the call to the compiler to test the -Og flag
(implied by cc-option) will be executed potentially for every C source
code file!

I think you need to use cc-option-add.

Ian.

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