Re: [PATCH] sim: common, microblaze, mn10300: handle signal.h defining REC_PC.

[Sam James <sam@gentoo.org>]

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> On 15 Jan 2023, at 00:22, Mike Frysinger <vapier@gentoo.org> wrote:
> 
> On 15 Jan 2023 00:28, Mark Wielaard wrote:
>> signal.h isn't needed in microblaze and mn10300 interp.c
>> so don't include it.
> 
> these changes are fine to merge if you want to split it out
> 
>> In common sim-events.c, sim-signal.c, nrun.c and dv-sockser.c we
>> do need signal.h, but check whether REG_PC is defined (and then
>> undefine it) before including the sim headers.
>> 
>> It breaks the build on sparc because signal.h indirectly
>> includes /usr/include/sys/ucontext.h and defines REG_PC,
>> which is also defined in microblaze-opcm.h
> 
> i don't think this is correct.  none of the files quoted use REG_PC,
> so undefining a random symbol in them doesn't make sense.  nothing in
> sim/common/ uses REG_PC for that matter.

The original error (https://builder.sourceware.org/buildbot/#/builders/229/builds/3) is:
```
In file included from ../../binutils-gdb/sim/mn10300/sim-main.h:41,
from ../../binutils-gdb/sim/common/dv-sockser.c:42:
../../binutils-gdb/sim/mn10300/mn10300-sim.h:68: error: "REG_PC" redefined [-Werror]
68 | #define REG_PC 9
|
In file included from /usr/include/signal.h:316,
from ../gnulib/import/signal.h:52,
from ../../binutils-gdb/sim/common/dv-sockser.c:29:
/usr/include/sys/ucontext.h:111: note: this is the location of the previous definition
111 | # define REG_PC (1)
|
```

There's history of just ducking this in other projects, and I can't really blame them:
https://patchwork.kernel.org/project/qemu-devel/patch/1490272961-1128-1-git-send-email-peter.maydell@linaro.org/

Overall, we have:
```
$ grep -rsin "#define.*REG_PC"
sim/mn10300/mn10300_sim.h:57:#define PC (State.regs[REG_PC])
sim/mn10300/mn10300_sim.h:74:#define REG_PC 9
gas/config/tc-arm.c:744:#define REG_PC  15
gprofng/libcollector/unwind.c:111:#define GET_PC(ctx) (((ucontext_t*)ctx)->uc_mcontext.gregs[REG_PC])
opcodes/microblaze-opcm.h:77:#define REG_PC_MASK 0x8000
opcodes/microblaze-opcm.h:101:#define REG_PC  32 /* PC.  */
include/opcode/cris.h:35:#define REG_PC (15)
include/opcode/cris.h:143:#define BDAP_PC_LOW     (BDAP_INDIR_LOW + REG_PC)
```

What do you prefer?

1. Rename all the REG_* (ugly)
2. #undef hack in each of the consumers where there's a #define for it?
3. What Mark did in some misc. top-level sim place
4. Beg every vendor to change their ucontext.h
5. Something else?

thanks,
sam


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