[OT] making software easily cross-compilable

Dave Korn dave.korn@artimi.com
Fri Apr 28 18:48:00 GMT 2006

On 28 April 2006 12:53, Robert P. J. Day wrote:

> On Fri, 28 Apr 2006, Dave Korn wrote:
>> On 28 April 2006 12:08, Robert P. J. Day wrote:
>>>   even more generally, the build process might need access to
>>> *both* the cross-compile tools and the native tools (like the
>>> linux kernel does), so you might see:
>>>   CC := ${CROSS_COMPILE}cc
>>>   LD := ${CROSS_COMPILE}ld
>>> and another set for the native tools:
>>>   HOSTCC = gcc
>>>   HOSTLD = ld
>>> etc.
>>   In GNU terms, these would be CC/LD and
> really?  i already knew that was another approach but it seems far
> more cumbersome.  it seems so much more straightforward to use the
> *generic* variables (CC, LD, ...) for *whatever* target you're
> building for, and have to *override* with HOSTCC, HOSTLD just in case
> you need to some native building.

  Actually I was thinking of CFLAGS_FOR_TARGET when I wrote that, I'm not
actually sure how the cross-tool names are defined.... let me just dig out an
old build log and take a look at the submake invocations.  Ah, here's a cygwin

make "AR_FLAGS=rc" 	"CC_FOR_BUILD=gcc" 	"CFLAGS=-O2 -g -O2 "
"INSTALL=/usr/bin/install -c" 	"LDFLAGS=" 	"LIBCFLAGS=-O2 -g -O2 "
"LIBCFLAGS_FOR_TARGET=-O2 -g -O2 " 	"MAKE=make" 	"MAKEINFO=makeinfo
--split-size=5000000 --split-size=5000000  " 	"PICFLAG="
"PICFLAG_FOR_TARGET=" 	"SHELL=/bin/sh" 	"EXPECT=expect"
"exec_prefix=/usr/build/install" 	"infodir=/usr/build/install/info"
"libdir=/usr/build/install/lib" 	"prefix=/usr/build/install"
"top_toollibdir=/usr/build/install/i686-pc-cygwin/lib" 	"AR=ar"
"AS=as" 	"CC=gcc -L/usr/build/obj-winsup/i686-pc-cygwin/winsup
-L/usr/build/obj-winsup/i686-pc-cygwin/winsup/w32api/lib -isystem
/usr/build/src-winsup/winsup/include -isystem
/usr/build/src-winsup/winsup/cygwin/include -isystem
-B/usr/build/obj-winsup/i686-pc-cygwin/newlib/ -isystem
/usr/build/obj-winsup/i686-pc-cygwin/newlib/targ-include -isystem
"LIBCFLAGS=-O2 -g -O2 " 	"NM=nm" 	"PICFLAG="
"RANLIB=ranlib" 	"DESTDIR=" DO=all multi-do # make

and here's one from a gcc build:

make GCC_FOR_TARGET="/repository/gcc-build/linux/gcc/gcc/xgcc
-B/repository/gcc-build/linux/gcc/gcc/ -B/artimi/tools/cygwin/arm-linux/bin/
-B/artimi/tools/cygwin/arm-linux/lib/ -isystem
/artimi/tools/cygwin/arm-linux/include" \
  AR_FOR_TARGET="arm-linux-ar" \
  AR_CREATE_FOR_TARGET="arm-linux-ar  rc" \
  CFLAGS="-g -O2 -W -Wall -Wwrite-strings -Wstrict-prototypes
-Wmissing-prototypes -Wtraditional -pedantic -Wno-long-long " \
  RANLIB_FOR_TARGET="arm-linux-ranlib" \
  RANLIB_TEST_FOR_TARGET="[ -f arm-linux-ranlib ] || ( [ "i686-pc-cygwin" =
"arm-unknown-linux-gnu" ] && [ -f /usr/bin/ranlib -o -f /bin/ranlib ] )" \
  NM_FOR_TARGET="/artimi/tools/cygwin/arm-linux/bin/nm.exe" AWK="gawk" \
  LIBGCC2_CFLAGS="-O2  -DIN_GCC -DCROSS_COMPILE   -W -Wall -Wwrite-strings
-Wstrict-prototypes -Wmissing-prototypes -isystem ./include
-fomit-frame-pointer -fPIC -g0 -DHAVE_GTHR_DEFAULT -DIN_LIBGCC2
  INCLUDES="-I. -I. -I/tools/external_source/gnu/gcc-3.3.3/gcc
-I/tools/external_source/gnu/gcc-3.3.3/gcc/../include" \
  CONFIG_H="tconfig.h " MACHMODE_H="machmode.h machmode.def
/tools/external_source/gnu/gcc-3.3.3/gcc/config/arm/arm-modes.def" \
  LIB1ASMSRC='arm/lib1funcs.asm' \
  -f libgcc.mk all

> doing it that way would certainly allow existing makefiles to be
> quickly cross-compilable.  i certainly wouldn't want to have to write
> new makefiles loaded with "_FOR_TARGET" suffixes everywhere.  barf.

  Well, autotools do all that for you.  Which is where we came in!

Can't think of a witty .sigline today....

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