Which macro to use when testing for target arhitecture?

[Dan Kegel]

Toralf Lund wrote:
> gcc typically defines at least 3 macros for build target architecture; 
> e.g. for m68k-coff-gcc, I have
> 
> #define __mc68000__ 1
> #define __mc68000 1
> #define mc68000 1
> 
> which one of these is the most appropriate to use when testing target 
> type within C code (using #ifdef or similar)?

Good question.  One tool you can use to explore this is to grep
the gcc sources for this define, e.g.

dank@dank:~/gnu/gcc/gcc/config/m68k$ grep mc68000 * | grep D

Notice that OpenBSD and Linux seem to define a mutually
exclusive set of symbols.  You may have to test for both, e.g.

#if defined(mc68000) || defined(__mc68000__)

- Dan

p.s. here's the output of that grep:

3b1g.h:#define CPP_PREDEFINES "-Dmc68000 -Dmc68k -Dunix -Dunixpc -Asystem=unix  -Asystem=svr3 -Acpu=m68k -Amachine=m68k"
ccur-GAS.h:    "-Dmc68000 -Dmasscomp -DMASSCOMP -Dunix -DLANGUAGE_C -Dconcurrent -DCONCURRENT"
crds.h:#define CPP_PREDEFINES "-Dmc68k -DM68000 -Dmc68000 -Dunos -Dunix -D__motorola__ -Asystem=unix  -Acpu=m68k -Amachine=m68k"
hp2bsd.h:#define CPP_PREDEFINES "-Dmc68000 -Dmc68010 -Dhp200 -Dunix -Asystem=unix -Asystem=bsd -Acpu=m68k -Amachine=m68k"
hp320.h:%{!ansi:%{!mc68000:%{!m68000:-Dmc68020}} -D_HPUX_SOURCE} -D__HPUX_ASM__"
hp320.h:%{!ansi:%{!mc68000:%{!m68000:-Dmc68020}} -D_HPUX_SOURCE} -D__HPUX_ASM__"
hp320.h:%{!ansi:%{!mc68000:%{!m68000:-Dmc68020}} -D_HPUX_SOURCE}"
hp320.h:%{!ansi:%{!mc68000:%{!m68000:-Dmc68020}} -D_HPUX_SOURCE}"
hp3bsd.h:#define CPP_PREDEFINES "-Dmc68000 -Dmc68020 -Dhp300 -Dhp9000 -Dunix -Asystem=unix  -Asystem=bsd -Acpu=m68k -Amachine=m68k"
hp3bsd44.h:#define CPP_PREDEFINES "-Dmc68000 -Dmc68020 -Dhp300 -Dhp9000 -Dunix -D__BSD_4_4__ -Asystem=unix  -Asystem=bsd -Acpu=m68k -Amachine=m68k"
linux-aout.h:  "-Dunix -Dmc68000 -Dmc68020 -D__gnu_linux__ -Dlinux -Asystem=unix -Asystem=posix -Acpu=m68k -Amachine=m68k"
linux.h:  "-D__ELF__ -Dunix -Dmc68000 -Dmc68020 -D__gnu_linux__ -Dlinux -Asystem=unix -Asystem=posix -Acpu=m68k -Amachine=m68k"
m68k-none.h:#define CPP_CPU_DEFAULT_SPEC "%{!ansi:-Dmc68000 } -D__mc68000 -D__mc68000__"
m68k-none.h:#define ASM_CPU_DEFAULT_SPEC "-mc68000"
m68k-none.h:#define CPP_PREDEFINES "-Dmc68000"
m68k-none.h:%{!mc68000:%{!m68000:%{!m68302:%{!mcpu32:%{!m68332:%{!m5200:%{!msoft-float:%{!mno-68881:%{!mfpa:%{!msky:-D__HAVE_68881__ }}}}}}}}}} \
m68k-psos.h:"%{!mc68000:%{!m68000:%{!m68332:%{!msoft-float:-D__HAVE_68881__ }}}}\
m68k-psos.h:%{!ansi:-Dmc68000 %{m68010:-Dmc68010 }%{m68020:-Dmc68020 }%{mc68020:-Dmc68020 }%{m68030:-Dmc68030 }%{m68040:-Dmc68040 }%{m68020-40:-Dmc68020 -Dmc68030 -Dmc68040 }%{m68302:-Dmc68302 
}%{m68332:-Dmc68332 }%{!mc68000:%{!m68000:%{!m68010:%{!mc68020:%{!m68020:%{!m68030:%{!m68040:%{!m68020-40:%{!m68302:%{!m68332:-Dmc68040 }}}}}}}}}}}\
m68k-psos.h:-D__mc68000__ -D__mc68000 %{m68010:-D__mc68010__ -D__mc68010 }%{m68020:-D__mc68020__ -D__mc68020 }%{mc68020:-D__mc68020__ -D__mc68020 }%{m68030:-D__mc68030__ -D__mc68030 
}%{m68040:-D__mc68040__ -D__mc68040 }%{m68020-40:-D__mc68020__ -D__mc68030__ -D__mc68040__ -D__mc68020 -D__mc68030 -D__mc68040 }%{m68302:-D__mc68302__ -D__mc68302 }%{m68332:-D__mc68332__ -D__mc68332 
}%{!mc68000:%{!m68000:%{!m68010:%{!mc68020:%{!m68020:%{!m68030:%{!m68040:%{!m68020-40:%{!m68302:%{!m68332:-D__mc68040__ -D__mc68040 }}}}}}}}}}"
m68kemb.h:#define CPP_PREDEFINES "-Dmc68000 -D__embedded__ -Asystem=embedded \
mot3300.h:%{!mc68000:%{!m68000: -D__mc68020__}}"
openbsd.h:#define CPP_PREDEFINES "-D__unix__ -D__m68k__ -D__mc68000__ -D__mc68020__ -D__OpenBSD__ -Asystem=unix -Asystem=OpenBSD -Acpu=m68k -Amachine=m68k"
rtemself.h:#define CPP_PREDEFINES "-Dmc68000 -D__rtems__ -D__ELF__ -D__USE_INIT_FINI__ \
sun2.h:#define CPP_PREDEFINES "-Dmc68000 -Dsun -Dunix -Asystem=unix  -Asystem=bsd -Acpu=m68k -Amachine=m68k"
sun3.h:%{m68000:-D__mc68010__}%{mc68000:-D__mc68010__}%{!mc68000:%{!m68000:-D__mc68020__}} \
sun3.h:%{!ansi:%{m68000:-Dmc68010}%{mc68000:-Dmc68010}%{!mc68000:%{!m68000:-Dmc68020}}}"
sun3.h:%{m68000:-D__mc68010__}%{mc68000:-D__mc68010__}%{!mc68000:%{!m68000:-D__mc68020__}} \
sun3.h:%{!ansi:%{m68000:-Dmc68010}%{mc68000:-Dmc68010}%{!mc68000:%{!m68000:-Dmc68020}}}"
sun3.h:#define CPP_PREDEFINES "-Dmc68000 -Dsun -Dunix -Asystem=unix  -Asystem=bsd -Acpu=m68k -Amachine=m68k"
sun3mach.h:#define CPP_PREDEFINES "-Dmc68000 -Dsun -Dsun3 -Dunix -DMACH -DCMU -DMTXINU -DBIT_MSF -DBYTE_MSF -Asystem=unix  -Asystem=mach -Acpu=m68k -Amachine=m68k"
vxm68k.h:#define CPP_PREDEFINES "-Dmc68000 -D__vxworks -D__vxworks_5 -Acpu=m68k -Amachine=m68k"

It looks like on


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