[Bug 2041] [1.16.2] "sed" segmentation fault

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=2041

--- Comment #2 from my.somewhat.lengthy.loginname at gmail.com  ---
(In reply to comment #1)
> Can you identify where exactly it segfaults in sed.c?

Alas not. Here is was I tried to get more details; no. 3 is perhaps the most
informative part.

(1) The "production" executable (compiled with my CFLAGS, stripped, etc.) says:

busybox[782]: segfault at 0 ip 08061e09 sp bf97ac88 error 4 in
busybox[8048000+187000]
Segmentation fault

(2) Then I unset all compiler-related environment flags and switched on "Build
BusyBox with extra Debugging symbols" in the "make menuconfig" dialogue, before
I compiled again. The error message from busybox_unstripped was similar;
interestingly the "ip" value was identical. I believe that "ip" here means
"instruction pointer," so I looked that up in busybox_unstripped.map. The
closest is

 .text          0x08061e00       0xe6 /usr/lib/libc.a(getc.o)
                0x08061e00                getc
                0x08061e00                _IO_getc
                0x08061e00                fgetc
 *fill*         0x08061ee6        0xa 90909090

(3) Next I switched on "Disable compiler optimizations" in the "make
menuconfig" dialogue, and compiled again. This time there was no segfault;
instead I got the expected output.

(4) I also tried my hands at GNU debugger, but it kept complaining about extra
command-line arguments.

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