[3.5] bpo-36478: Use C89 for loops in backported pickle patch by asottile · Pull Request #12622

[3.5] bpo-36478: Use C89 for loops in backported pickle patch by asottile · Pull Request #12622 · python/cpython

I tried gcc -std=c89, the compiler fails early on a different file:

gcc -pthread -c -Wno-unused-result -Wsign-compare -g -Og -Wall -Wstrict-prototypes -std=c89   -Werror=declaration-after-statement   -I. -I./Include    -DPy_BUILD_CORE -o Objects/listobject.o Objects/listobject.c
Objects/bytesobject.c: In function '_PyBytes_Format':
Objects/bytesobject.c:782:17: error: C++ style comments are not allowed in ISO C90
                 // %r is only for 2/3 code; 3 only code should use %a
                 ^
Objects/bytesobject.c:782:17: error: (this will be reported only once per input file)

This comment was added 4 years ago:

commit 62e977f1b6d52a973304db9b0268aece99cb6c42
Author: Ethan Furman <ethan@stoneleaf.us>
Date:   Wed Mar 11 08:17:00 2015 -0700

    Close issue23467: add %r compatibility to bytes and bytearray

I'm not sure which kind of problem we are trying to solve here.

I know that on Windows, "error: 'for' loop initial declarations are only allowed in C99 mode" might be an error, but at this point, nobody tried to build the latest Python 3.5 on Windows and the compilation goes fine on Linux with default GCC flags. There issue looks to be specific to compiler flags used by https://github.com/deadsnakes