Hello,
I had a problems with generating code with many jumps.
I've managed to narrow it down to following test case, it causes
invalid memory access:
(this is based on luajit 2.0.4)
```
|.arch x64
|.section code
|.globals GLOB_
|.actionlist actions
#include "dasm_x86.h"
#include <stdio.h>
void dynasmGenerator(Dst_DECL, int nopCount)
{
int labelsCount = 1;
dasm_growpc(Dst, labelsCount + nopCount);
printf("labels count: %d\n", labelsCount);
for (int i = 0; i < nopCount; ++i) {
| jmp => (i + 1)
| =>(i + 1):
}
| xor rax, rax
| mov rax, 0x12345678ull
| shl rax, 32
| or rax, 0x09abcdefull
| ret
printf("zomg, aot done");
}
```
(and here's some boiler plate code I'm using: http://ideone.com/pWUn7g)
it's fine, when called like:
generate(&dasmState, 4 * 1024 * 1024 + 0)
but just adding 1, yields an error:
generate(&dasmState, 4 * 1024 * 1024 + 1)
invalid access happens in inside dasm_put, in case DASM_LABEL_PC
```
while (n > 0) {
int *pb = DASM_POS2PTR(D, n); // 1
n = *pb; // 2 invalid access
*pb = pos; // 3
}
```
DASM_POS2PTR(D, n) expands to (D->sections[DASM_POS2SEC(pos)].rbuf + pos).
at the beginning of dasm_put, section is expanded, but only rbuf of "current"
section is altered:
if (pos >= sec->epos) {
DASM_M_GROW(Dst, int, ...
sec->rbuf = sec->buf - DASM_POS2BIAS(pos);
result of DASM_POS2SEC(pos) in this case is 1, and value of rbuf for section[1]
is the one that is set in dasm_init:
for (i = 0; i < maxsection; i++) {
D->sections[i].buf = NULL; /* Need this for pass3. */
D->sections[i].rbuf = D->sections[i].buf - DASM_SEC2POS(i);
Now, I'm not sure how section handling should work, so I don't know how fix
should look like
--
main (int a, char *b[puts("Michal 'GiM' Spadlinski")]) {}
