On Thursday, 7 March 2013 at 01:25:02 UTC, Walter Bright wrote:
Some months ago, I did make the source to optlink available on
github:
https://github.com/DigitalMars/optlink
Rainer Schuetze has improved it where it can be built with
modern tools (the older tools would not run on Win7). I know
some of you are frustrated by optlink problems. Well, now you
can do something about it!
Note that the optlink source is quite a challenge to work on.
It's very old skool (80's style).
Here's an approach that I've used successfully to fix optlink
seg faults:
1. Find out where in the source code it is. This is not so
easy, even if using a debugger. The trouble is the asm
functions do not have standard stack frames, so the debugger
cannot do a stack trace. Even where there is a standard stack
frame, the modern Microsoft debuggers fail to recognize them.
You gotta use an older debugger under Windows XP.
So, what I do, is look at the asm code where the seg fault
occurs, and then grep through the asm source till I find it.
2. Convert the source file where the seg fault occurs to C. I
do this one function at a time, running the full set of tests
at each step. Otherwise, it's just impossible to figure out
where you made a mistake in the conversion. Sometimes, you
gotta go even finer grained - using the inline assembler
feature of dmc to convert asm code line by line.
You gotta pay very, very close attention to which registers
have parameters passed through them, which registers are saved,
and which registers have parameters that are silently passed
through a function to callees of that function (!). This
information is all pretty much utterly lacking in the comments,
and the comments are often dead wrong as they refer to much
older versions of the code.
3. Once it is in C, things get a lot easier. You can, for
example, insert printf's to figure out where things go wrong,
and *then* fix it.
The full test suite for optlink has a lot of stuff I cannot
publish on github. However, what you can do is run the win32
tests for dmd. I, of course, will run the full one when
verifying pulls.
Happy hacking!
Is this the current linker used by DMD on all platforms?
