[Bug c++/70495] New: false warning: comparison between signed and unsigned integer expressions

[andras.szilard at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70495

            Bug ID: 70495
           Summary: false warning: comparison between signed and unsigned
                    integer expressions
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: andras.szilard at gmail dot com
  Target Milestone: ---

Hi,
I have the strange warning "comparison between signed and unsigned integer
expressions" when only unsigned types are used (more than 2 members).

Simplest example (I could find):
uint32_t a = 0;
uint8_t b = 0;
a < b + b + b;

Some more details: http://coliru.stacked-crooked.com/a/816fde87f946dcad

Side notes:
- Originally I used size_t instead of uint32_t (as in my real-life code).
- Using uint16_t instead of uint32_t / size_t does not give this warning.
- clang++ does not give this warning.

Tested the sample code with these g++ compiler versions: 4.8.4, 5.3.0 and
5.3.1.

Please, clarify what is going on! :)
Thanks in advance!