Hello,
 
When compiling simple test programs with -g3 and input from the console (- (stdin)), the .debug_line section is wrong. 

Steps to reproduce this issue: 

1. In your console type:

arm-none-eabi-gcc -mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16 -O0 -g3 -c -o test.o -x c -

2. Copy and paste: 

#include <stdio.h>
int main(void)
{
	printf("Hello World\n");
	return 0;
}

3. Ctrl+Z and Return 

4. If you type: arm-none-eabi-readelf --debug-dump=decodedline  test.o
You get the following:

Contents of the .debug_line section:

CU: ./<stdin>:
File name                            Line number    Starting address    View
readelf: Warning: Badly formed extended line op encountered!
readelf: Warning: Badly formed extended line op encountered!
UNKNOWN (116): length 115
<stdin>                                        0                 0xc
<stdin>                                       -1                0x1a
<stdin>                                       -1                0x1e
<stdin>                                        1                0x2a
UNKNOWN (0): length 4
<stdin>                                       -1                0x36
<stdin>                                       -6                0x42
<stdin>                                       -8                0x50
<stdin>                                       -7                0x5c
<stdin>                                       -7                0x60
<stdin>                                       -5                0x6c
UNKNOWN (0): length 2
<stdin>                                        2                0x76
<stdin>                                        2                0x84
<stdin>                                        7                0x92
<stdin>                                        3                0xa0
<stdin>                                        2                0xac
<stdin>                                        1                0xba
<stdin>                                        1                0xbe
<stdin>                                        3                0xca
UNKNOWN (0): length 4
<stdin>                                       -1                0xd8
<stdin>                                       -2                0xe4
<stdin>                                       -3                0xf2
<stdin>                                       -3                0xf6
<stdin>                                       -1               0x102
UNKNOWN (0): length 1
UNKNOWN (115): length 95
<stdin>                                       -2               0x110
<stdin>                                       -6               0x11e
<stdin>                                       -7               0x12a
<stdin>                                      -10               0x136
<stdin>                                      -10               0x13a
<stdin>                                       -8               0x146
UNKNOWN (0): length 1
UNKNOWN (112): length 95

5. Repeating the steps with -g instead of -g3 we get the right .debug_line section:
Contents of the .debug_line section:

CU: ./<stdin>:
File name                            Line number    Starting address    View
<stdin>                                        3                   0
<stdin>                                        4                 0x4
<stdin>                                        5                 0xa
<stdin>                                        6                 0xc
<stdin>                                        6                0x14