[Buildroot] CFLAGS_FOR_BUILD compiler flags

[Buildroot] CFLAGS_FOR_BUILD compiler flags

[Will Newton]

Hi all,

It looks like something changed with the flags passed when building
toolchains. In older buildroots it seems we passed "-g -O2"
explicitly:

$ grep CFLAGS_FOR_BUILD toolchain/gcc/gcc-uclibc-3.x.mk
CFLAGS_FOR_BUILD="-g -O2 $(HOST_CFLAGS)" \
CFLAGS_FOR_BUILD="-g -O2 $(HOST_CFLAGS)" \
CFLAGS_FOR_BUILD="-g -O2 $(HOST_CFLAGS)" \

Now we use TARGET_CONFIGURE_OPTS, which sets CFLAGS_FOR_BUILD for us:

$ grep CFLAGS_FOR_BUILD package/Makefile.in
CFLAGS_FOR_BUILD="$(HOST_CFLAGS)" \
FCFLAGS_FOR_BUILD="$(HOST_FCFLAGS)" \

But without the -g -O2 being added. This results in the toolchain
being built without optimisations, which makes it a bit slower than it
otherwise would be (although I expect it makes building the toolchain
faster!).

CFLAGS_FOR_BUILD is currently defaulted in the top-level Makefile but
then not used. Perhaps a patch like the below would be the right thing
to do? Comments?

---

Set a default set of flags (-g -O2) for the host tools, this
prevents the tools from being built without optimisation which
improves build times considerably.

Signed-off-by: Will Newton <will.newton@imgtec.com>
---
 Makefile |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 462d974..c711f22 100644
--- a/Makefile
+++ b/Makefile
@@ -144,14 +144,14 @@ HOSTLD:=$(shell which $(HOSTLD) || type -p
$(HOSTLD) || echo ld)
 HOSTLN:=$(shell which $(HOSTLN) || type -p $(HOSTLN) || echo ln)
 HOSTNM:=$(shell which $(HOSTNM) || type -p $(HOSTNM) || echo nm)

-ifndef CFLAGS_FOR_BUILD
-CFLAGS_FOR_BUILD:=-g -O2
+ifndef HOST_CFLAGS
+HOST_CFLAGS:=-g -O2
 endif
-ifndef CXXFLAGS_FOR_BUILD
-CXXFLAGS_FOR_BUILD:=-g -O2
+ifndef HOST_CXXFLAGS
+HOST_CXXFLAGS:=-g -O2
 endif
-ifndef FCFLAGS_FOR_BUILD
-FCFLAGS_FOR_BUILD:=-g -O2
+ifndef HOST_FCFLAGS
+HOST_FCFLAGS:=-g -O2
 endif
 export HOSTAR HOSTAS HOSTCC HOSTCXX HOSTFC HOSTLD

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[Buildroot] CFLAGS_FOR_BUILD compiler flags

[Peter Korsgaard]

>>>>> "Will" == Will Newton <will.newton@gmail.com> writes:

 Will> Hi all,
 Will> It looks like something changed with the flags passed when building
 Will> toolchains. In older buildroots it seems we passed "-g -O2"
 Will> explicitly:

 Will> $ grep CFLAGS_FOR_BUILD toolchain/gcc/gcc-uclibc-3.x.mk
 Will> CFLAGS_FOR_BUILD="-g -O2 $(HOST_CFLAGS)" \
 Will> CFLAGS_FOR_BUILD="-g -O2 $(HOST_CFLAGS)" \
 Will> CFLAGS_FOR_BUILD="-g -O2 $(HOST_CFLAGS)" \

 Will> Now we use TARGET_CONFIGURE_OPTS, which sets CFLAGS_FOR_BUILD for us:

 Will> $ grep CFLAGS_FOR_BUILD package/Makefile.in
 Will> CFLAGS_FOR_BUILD="$(HOST_CFLAGS)" \
 Will> FCFLAGS_FOR_BUILD="$(HOST_FCFLAGS)" \

 Will> But without the -g -O2 being added. This results in the toolchain
 Will> being built without optimisations, which makes it a bit slower than it
 Will> otherwise would be (although I expect it makes building the toolchain
 Will> faster!).

 Will> CFLAGS_FOR_BUILD is currently defaulted in the top-level Makefile but
 Will> then not used. Perhaps a patch like the below would be the right thing
 Will> to do? Comments?

You're completely right. I prefer to get rid of CFLAGS_FOR_BUILD though
as it's only used by sstrip, so I've committed a slightly different patch.

-- 
Bye, Peter Korsgaard