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c++ - using Lua

reply "Eduardo Nunes" <edfpn hotmail.com> writes:
Hi,

Does anyone have compile/use Lua-5.0 package with DMC ?

When compiling Lua with switches (-o or -o+all), I think the compiler(beta
v834)
produces wrong code (win32 code).
It's fine without optimization and with other compilers.
I can't reproduce the problem outside Lua. so the 'smallest exemples',
it's not that small :-(

http://www.sky3d.com/bug1.zip (~82k)

Only need to unzip to a directory and run smake.

The problem lies in file lvm.c, line 328, function luaV_concat.
/*--- begin code ---*/
while (n < total && tostring(L, top-n-1)) {  /* collect total length */
  tl += tsvalue(top-n-1)->tsv.len;
  n++;
}
/*--- end code ---*/
tl compute the length of all strings, but in the 'while' compiled code,
tl don't have the correct value.

i.e., the code loops the same amount of times and in the same manner as in
the
unoptimized code, but at exit, the tl value isn't the same.

tl is not in memory. I think tl is assign to a register, but none have
the correct tl value inside the loop.

as result, the destination string will be allocate with the wrong size
value.
(luaZ_openspace will call realloc(NULL, tl))
/*--- begin code ---*/
buffer = luaZ_openspace(L, &G(L)->buff, tl);
tl = 0;
for (i=n; i>0; i--) {  /* concat all strings */
  size_t l = tsvalue(top-i)->tsv.len;
  memcpy(buffer+tl, svalue(top-i), l);
  tl += l;
}
/*--- end code --*/
and will write pass end of this buffer, corrupting the heap and crash
the any program, down the road.

Looks like a register allocation / assignment problem, it's very hard to
reproduce
the register pressure up to this point in source code, to isolate no a very
small example.

any help ?

Thanks.

Eduardo Nunes
edfpn hotmail.com
May 09 2003
parent "Luna Kid" <lunakid neuropolis.org> writes:
Could you please notify me, too, if this gets settled?

(I compiled Lua 5.0 with DMC but not run it much yet.)

Thanks,
Sz.


"Eduardo Nunes" <edfpn hotmail.com> wrote in message
news:b9fv71$2uc5$1 digitaldaemon.com...
 Hi,

 Does anyone have compile/use Lua-5.0 package with DMC ?

 When compiling Lua with switches (-o or -o+all), I think the compiler(beta
 v834)
 produces wrong code (win32 code).

May 12 2003