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INT 21h: Add option whether to assign MCB ownership or return an error if a DOS program attempts to resize a freed memory block. Fix DOS resize to assign ownership even if the MCB is already the size requested to resize to.

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This commit is contained in:
Jonathan Campbell
2024-04-16 12:39:17 -07:00
parent 2d4fedd5ed
commit 641c69600a
4 changed files with 27 additions and 1 deletions
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14
src/dos/dos_memory.cpp
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@@ -333,6 +333,7 @@ bool DOS_AllocateMemory(uint16_t * segment,uint16_t * blocks) {
return false;
}
extern bool freed_mcb_allocate_on_resize;
bool DOS_ResizeMemory(uint16_t segment,uint16_t * blocks) {
if (segment < DOS_MEM_START+1) {
@@ -349,6 +350,13 @@ bool DOS_ResizeMemory(uint16_t segment,uint16_t * blocks) {
return false;
}
if (mcb.GetPSPSeg()==MCB_FREE && !freed_mcb_allocate_on_resize) {
*blocks=0;
DOS_SetError(DOSERR_MCB_DESTROYED);
LOG(LOG_DOSMISC,LOG_DEBUG)("DOS application attempted to resize freed memory block at segment 0x%x",(unsigned int)segment);
return false;
}
uint16_t total=mcb.GetSize();
DOS_MCB mcb_next(segment+total);
@@ -359,7 +367,10 @@ bool DOS_ResizeMemory(uint16_t segment,uint16_t * blocks) {
if (*blocks<=total) {
if (GCC_UNLIKELY(*blocks==total)) {
/* Nothing to do */
/* Nothing to do, however if the block is freed, canonical MS-DOS behavior is to assign your PSP segment as if allocated (Incentiv by DID, party '94) */
if (mcb.GetPSPSeg()==MCB_FREE && freed_mcb_allocate_on_resize)
mcb.SetPSPSeg(dos.psp());
return true;
}
/* Shrinking MCB */
@@ -405,6 +416,7 @@ bool DOS_ResizeMemory(uint16_t segment,uint16_t * blocks) {
/* adjust type of joined MCB */
mcb.SetType(mcb_next.GetType());
}
mcb.SetSize(total);
mcb.SetPSPSeg(dos.psp());
if (*blocks==total) return true; /* block fit exactly */