Re: Having hard time adding to CFLAGS

[Szabolcs Nagy <nsz@port70.net>]

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* Denys Vlasenko <vda.linux@googlemail.com> [2015-10-23 00:31:09 +0200]:
> Let's say I need to add a gcc option to my musl build.
> 
> configure says:
> ...
> Some influential environment variables:
>   CC                      C compiler command [detected]
>   CFLAGS                  C compiler flags [-Os -pipe ...]
>   CROSS_COMPILE           prefix for cross compiler and tools [none]
>   LIBCC                   compiler runtime library [detected
> 
> So I try this, combining all possible ways of passing CFLAGS
> (past experience is that different projects do it differently).
> 
> CFLAGS is in environment, and on both configure and make
> command lines:
> 
> export CFLAGS="-falign-functions=1"    # for example
> ./configure CFLAGS="$CFLAGS"
> make CFLAGS="$CFLAGS"

this is not what configure said...

> Evidently, my CFLAGS replaced needed flags instead of being added at the end.
> 
> Can this be fixed? If user needs to use e.g. EXTRA_CFLAGS instead,
> please fix configure --help.

it can be fixed, but i think 'needed flag' is not
always clear and overriding CFLAGS on the make
commandline is not polite.

the attached patch makes this work, but i
consider -Os to be not part of 'needed'

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diff --git a/Makefile b/Makefile
index 844a017..f713286 100644
--- a/Makefile
+++ b/Makefile
@@ -94,22 +94,22 @@ crt/crt1.o crt/Scrt1.o crt/rcrt1.o src/ldso/dlstart.lo: $(wildcard arch/$(ARCH)/
 
 crt/rcrt1.o: src/ldso/dlstart.c
 
-crt/Scrt1.o crt/rcrt1.o: CFLAGS += -fPIC
+crt/Scrt1.o crt/rcrt1.o: CFLAGS_ALL += -fPIC
 
 OPTIMIZE_SRCS = $(wildcard $(OPTIMIZE_GLOBS:%=src/%))
-$(OPTIMIZE_SRCS:%.c=%.o) $(OPTIMIZE_SRCS:%.c=%.lo): CFLAGS += -O3
+$(OPTIMIZE_SRCS:%.c=%.o) $(OPTIMIZE_SRCS:%.c=%.lo): CFLAGS_ALL += -O3
 
 MEMOPS_SRCS = src/string/memcpy.c src/string/memmove.c src/string/memcmp.c src/string/memset.c
-$(MEMOPS_SRCS:%.c=%.o) $(MEMOPS_SRCS:%.c=%.lo): CFLAGS += $(CFLAGS_MEMOPS)
+$(MEMOPS_SRCS:%.c=%.o) $(MEMOPS_SRCS:%.c=%.lo): CFLAGS_ALL += $(CFLAGS_MEMOPS)
 
 NOSSP_SRCS = $(wildcard crt/*.c) \
 	src/env/__libc_start_main.c src/env/__init_tls.c \
 	src/thread/__set_thread_area.c src/env/__stack_chk_fail.c \
 	src/string/memset.c src/string/memcpy.c \
 	src/ldso/dlstart.c src/ldso/dynlink.c
-$(NOSSP_SRCS:%.c=%.o) $(NOSSP_SRCS:%.c=%.lo): CFLAGS += $(CFLAGS_NOSSP)
+$(NOSSP_SRCS:%.c=%.o) $(NOSSP_SRCS:%.c=%.lo): CFLAGS_ALL += $(CFLAGS_NOSSP)
 
-$(CRT_LIBS:lib/%=crt/%): CFLAGS += -DCRT
+$(CRT_LIBS:lib/%=crt/%): CFLAGS_ALL += -DCRT
 
 # This incantation ensures that changes to any subarch asm files will
 # force the corresponding object file to be rebuilt, even if the implicit