Compiler repotrs overflow warning when compiling otp_src_27.2.2

Questions / Help
1

please excuse if i posted to a wrong category.

i’m a bit concerned because when compiling otp_src_27.2.2 the following warning is reported by gcc:

CC     obj/aarch64-unknown-linux-gnu/opt/jit/dist.o
In file included from ../include/internal/gcc/ethread.h:347,
                 from ../include/internal/ethread.h:389,
                 from beam/erl_threads.h:252,
                 from beam/sys.h:539,
                 from beam/dist.c:37:
In function 'ethr_native_atomic64_set_relb',
    inlined from 'ethr_atomic_set_mb' at ../include/internal/ethr_atomics.h:4019:5,
    inlined from 'erts_dist_command' at beam/dist.c:3867:5:
../include/internal/gcc/ethr_atomic.h:144:5: warning: '__atomic_store_8' writing 8 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
  144 |     __atomic_store_n(&var->value, value, __ATOMIC_RELEASE);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

question: is it safe to ignore this warning?

2

I also get this with gcc-14.2 on aarch64-linux-gnu. gcc has had false warnings before, and I believe this one is too, but I can’t prove that right now.

3

compiled with gcc.14.2.0-6 on x86_64-linux-gnu and the warning this not emitted.

4

It does look like a gcc bug. I’ve reduced the preprocessed code for dist.c on aarch64-linux-gnu to a 42 line test case that triggers this warning on both aarch64 and x86_64. Small code changes that don’t change the semantics of the source silence the warning.

5

There are two bugs:

  1. On the gcc side, the warning is valid, but the message is misleading and it doesn’t always trigger as it should. There’s a gcc upstream bug report about that.
  2. On the BEAM side, there is a missing NULL pointer check in the source code. However, it appears that it “cannot” happen at runtime. There is a pull request on GH now to silence the warning.

You can ignore the warning.

2 Likes
6

thank you very much for your efforts.

should i close this topic?

7

should i close this topic?

Yes please.