gdb not stopping at even trivial breakpoints - ffmpeg

Question

I am trying to debug ffplay (a debug build) compiled using mingw-w64 on msys2 on Windows 7 64bit. I tried setting breakpoints using gdb, and they seem to be set fine, but the program does not stop. So i tried issuing start, and again it didn't stop. I tried manually setting a breakpoint at main, but it still didn't stop. I verified that main is found, and it is. Here is a portion of the session. Any explanation what might cause this?
(gdb) start
Temporary breakpoint 1 at 0x140013f7c: file C:/Users/bubaruch/Documents/projects/ffmpeg/ffmpeg/ffplay.c, line 3756.
Starting program: C:\Users\bubaruch\Documents\projects\ffmpeg\b2\ffplay_g.exe
[New Thread 7752.0x275c]
ffplay version 2.8.git Copyright (c) 2003-2015 the FFmpeg developers
built with gcc 5.2.0 (Rev4, Built by MSYS2 project)
configuration: --disable-doc --disable-optimizations
libavutil 55. 5.100 / 55. 5.100
libavcodec 57. 15.100 / 57. 15.100
libavformat 57. 14.100 / 57. 14.100
libavdevice 57. 0.100 / 57. 0.100
libavfilter 6. 15.100 / 6. 15.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
Simple media player
usage: ffplay [options] input_file
An input file must be specified
Use -h to get full help or, even better, run 'man ffplay'
[Inferior 1 (process 7752) exited with code 01]
(gdb) l main
3748 return 1;
3749 }
3750
3751 /* Called from the main */
3752 int main(int argc, char **argv)
3753 {
3754 int flags;
3755 VideoState *is;
3756 char dummy_videodriver[] = "SDL_VIDEODRIVER=dummy";
3757
(gdb) b main
Breakpoint 2 at 0x140013f7c: file C:/Users/bubaruch/Documents/projects/ffmpeg/ffmpeg/ffplay.c, line 3756.
(gdb) r
Starting program: C:\Users\bubaruch\Documents\projects\ffmpeg\b2\ffplay_g.exe
[New Thread 15388.0x3278]
ffplay version 2.8.git Copyright (c) 2003-2015 the FFmpeg developers
built with gcc 5.2.0 (Rev4, Built by MSYS2 project)
configuration: --disable-doc --disable-optimizations
libavutil 55. 5.100 / 55. 5.100
libavcodec 57. 15.100 / 57. 15.100
libavformat 57. 14.100 / 57. 14.100
libavdevice 57. 0.100 / 57. 0.100
libavfilter 6. 15.100 / 6. 15.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
Simple media player
usage: ffplay [options] input_file
An input file must be specified
Use -h to get full help or, even better, run 'man ffplay'
[Inferior 1 (process 15388) exited with code 01]

Answer 1

From docs:
The ‘start’ command does the equivalent of setting a temporary
breakpoint at the beginning of the main procedure and then invoking
the ‘run’ command.
So you're already inside main when you set the breakpoint. It is never reached again, since the program exits at the end of main. Thus, the breakpoint never triggers.
I have the feeling you're trying to set alternate breakpoints deep inside ffmpeg and debug something more specific, and that's not triggering either. Why don't you ask that question instead? The explanation for it is likely very different, probably having to do with inlining.

Answer 2

Perhaps the symbols file is out-of-sync with the executable.
gdb tells you that main() is at line 3756. On my system it'd tell you it's at line 3753 (on the "{" line). Maybe somebody edited the source files and compiled it but hasn't re-created the symbols file, thereby making gdb setting breakpoints at unreachable addresses.