Bug#862858: gcc-6.3.0 produces binary that gdb cannot automatically reload when it changes
Upon further investigation, the bug I encountered is rather with gdb than
gcc.
gdb does not seem to cope very well with position-independent
executables. Reloading a PIE file gets the entry point wrong.
Example below. Notice how the first time gdb seems a PIE executable (when
a.out has gone PIE compared to the previous one which wasn't), things go
well. Problem is on the second load.
cassoulet /tmp $ gdb
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(gdb) shell gcc-6 -W -Wall -g -no-pie a.c
(gdb) file a.out
Reading symbols from a.out...done.
(gdb) b a
Breakpoint 1 at 0x4004fa: file a.c, line 5.
(gdb) r
Starting program: /tmp/a.out
Breakpoint 1, a () at a.c:5
5 printf("Hello, world\n");
(gdb) shell gcc-6 -W -Wall -g -no-pie a.c
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
`/tmp/a.out' has changed; re-reading symbols.
Starting program: /tmp/a.out
Breakpoint 1, a () at a.c:5
5 printf("Hello, world\n");
(gdb) shell gcc-6 -W -Wall -g -fPIE -pie a.c
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
`/tmp/a.out' has changed; re-reading symbols.
Starting program: /tmp/a.out
Breakpoint 1, a () at a.c:5
5 printf("Hello, world\n");
(gdb) shell gcc-6 -W -Wall -g -fPIE -pie a.c
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
`/tmp/a.out' has changed; re-reading symbols.
Error in re-setting breakpoint 1: Cannot access memory at address 0x5555555546b0
Starting program: /tmp/a.out
Hello, world
[Inferior 1 (process 24316) exited normally]
(gdb)
E.
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