In the debug info for a program, the end address for each segment that a file contributes to is set to the starting address of the last line in the segment, not the very last address in the segment.
The end address of segments that a whole compiland contributes to is set correctly, though.
This applies to the sstSrcModule record type. In the following example, the executable base is 402000h:
Compiland #1
Name: 'd.obj'
Section count: 1
File count: 7
Segment #2
Start offset: 00000010
End offset: 00004185
File #0
Name: 'F:\dmd.2.045\dmd2\windows\bin\..\..\src\phobos\std\format.d'
...
Segment #2
Start offset: 00003e64
End offset: 00004182 (*should be 4185)
Line count: 57
Line 0: 00003e64, 2175
Line 1: 00003e6e, 2180
...
Line 55: 0000415a, 2124
Line 56: 00004182, 2131
...
File #6
Name: 'd.d'
Segment count: 1
Segment #2
Start offset: 00000010
End offset: 00000236 (*should be 23c)
Line count: 51
Line 0: 00000010, 20
Line 1: 0000001f, 22
...
Line 49: 00000222, 92
Line 50: 00000236, 93
This compiland contributes to section 2 between offsets 10h and 4185h. Here's one example of the problem. At the end of the compiland contribution, there's the pair of instructions below. Instead of the segment contribution saying that it goes all the way to the end of the ret instruction, it says it goes to the beginning of the leave:
[offset 4182]
0x00004d82 0x00406182 0xc9 leave esp,ebp
0x00004d83 0x00406183 0xc2,0x04,0x00 ret 0x4
The same thing happens for a function in a segment contribution in the middle of the compiland contribution:
[offset 236]
0x00000e36 0x00402236 0x5f pop edi
0x00000e37 0x00402237 0x5e pop esi
0x00000e38 0x00402238 0x5b pop ebx
0x00000e39 0x00402239 0xc9 leave esp,ebp
0x00000e3a 0x0040223a 0xc2,0x04,0x00 ret 0x4
Comment #1 by aldonunez1 — 2011-04-19T11:44:29Z
When debugging in source code view, you reach the return statement of a function. Then you step over to try to return to the caller. Instead, we're put into disassembly to step thru the epilogue of the function.
This seems to be a problem in the linker. I couldn't find where in the compiler this wrong information is set. I suspect that when the linker makes the sstSrcModule record, it uses the offset of the last line, instead of the offset of the last byte of the function it's in.
Comment #2 by robert.schadek — 2024-12-13T17:53:18Z