[Bug c/126702] New: undefined reference to inline function

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126702

            Bug ID: 126702
           Summary: undefined reference to inline function
           Product: gcc
           Version: 16.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antonio at gnu dot org
  Target Milestone: ---
              Host: i586, x86_64

Created attachment 65262
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65262&action=edit
24-line source file that reproduces the problem

While building clzip-1.0 I got the following error:
main.c:(.text.startup+0x34c): undefined reference to `resize_buffer'

I have reduced the code to a single 24-line file that reproduces the problem
when compiled with:
gcc -c -o main.o main.c && gcc -o clzip main.o

The function 'resize_buffer' is marked 'inline', but gcc neither inlines it nor
compiles it into main.o. This is the output of 'nm main.o':
00000000 T ap_resize_buffer
00000000 B gbuf
00000015 T main
         U resize_buffer

The bug is present (at least) in versions 16.1.0, 11.2.0, and 10.5.0. Tested on
three different machines with different GCC configurations.