dlmalloc_ext_2_8_6.c:1085:41: warning: iteration 2305843009213693951 invokes undefined behavior [-Waggressive-loop-optimizations]

[mojca]

I'm building a project with boost 1.80.0 as an external dependency, obtained via FetchContent as part of a CMake build. I'm using gcc-12 on Ubuntu-22.04 and we are trying to get "treat warnings as errors" builds go through.

This is the warning I get:

[1/675] Building C object _deps/boost-build/libs/container/CMakeFiles/boost_container.dir/src/alloc_lib.c.o
In file included from ../__external/src/boost/libs/container/src/dlmalloc_ext_2_8_6.c:52,
                 from ../__external/src/boost/libs/container/src/alloc_lib.c:24:
In function ‘internal_multialloc_arrays’,
    inlined from ‘boost_cont_multialloc_arrays’ at ../__external/src/boost/libs/container/src/dlmalloc_ext_2_8_6.c:1112:13:
../__external/src/boost/libs/container/src/dlmalloc_ext_2_8_6.c:1085:41: warning: iteration 2305843009213693951 invokes undefined behavior [-Waggressive-loop-optimizations]
 1085 |                size = request2size(sizes[i]*element_size);
      |                                         ^
../__external/src/boost/libs/container/src/dlmalloc_2_8_6.c:2231:6: note: in definition of macro ‘request2size’
 2231 |   (((req) < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(req))
      |      ^~~
../__external/src/boost/libs/container/src/dlmalloc_ext_2_8_6.c:1083:24: note: within this loop
 1083 |             for(++i; i != next_i; ++i) {
      |                      ~~^~~~~~~~~