Buildroot error when building with Ubuntu 21.10

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I am trying to compile linux for RISCV Arch using buildroot(busybox). I was using 18.04 and 20.04 previously and had no issues compiling it. Right now, I have upgraded it to 21.10 for building some other stuffs. I have moved my toolchain and I can find it using the which command. When I try to compile linux I get some error which I havn't faced in the earlier versions.

>>> host-m4 1.4.18 Building

In file included from /usr/include/signal.h:328,
                 from ./signal.h:52,
                 from c-stack.c:49:
c-stack.c:55:26: error: missing binary operator before token "("
   55 | #elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
      |                          ^~~~~~~~
  CC       closein.o
c-stack.c:134:8: error: variably modified 'buffer' at file scope
  134 |   char buffer[SIGSTKSZ];
      |        ^~~~~~
  CC       closeout.o

I am confused on how different versions can cause this error.

Thanks in advance.

buildroot riscv busybox linux-kernel
1 Answers

It looks like you have hit a change in GNU C Library version 2.34 that can make SIGSTKSZ non-constant.

From the GNU C Library 2.34 release announcement:

  • Add _SC_MINSIGSTKSZ and _SC_SIGSTKSZ. When _DYNAMIC_STACK_SIZE_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ are no longer constant on Linux. MINSIGSTKSZ is redefined to sysconf(_SC_MINSIGSTKSZ) and SIGSTKSZ is redefined to sysconf (_SC_SIGSTKSZ). This supports dynamic sized register sets for modern architectural features like Arm SVE.

A possible workaround is to configure buildroot to build host-m4 version 1.4.19 instead of 1.4.18, because it no longer uses SIGSTKSZ.

user_52644910
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