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Add support for unions

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Unions allow multiple memory allocations (using ds, etc.) to share the
same space in memory.

This allows games to use the same memory for different purposes,
depending on their state.

This also adds documentation on how to use the new UNION, NEXTU, and
ENDU keywords.
This commit is contained in:
Ben10do
2017-07-20 19:17:03 +01:00
committed by Antonio Niño Díaz
parent 4d01b2d5ac
commit f8bbe9be48
6 changed files with 132 additions and 7 deletions
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24
src/asm/output.c
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@@ -460,6 +460,8 @@ checkcodesection(void)
pCurrentSection->nType != SECT_ROMX) {
fatalerror("Section '%s' cannot contain code or data (not ROM0 or ROMX)",
pCurrentSection->pzName);
} else if (nUnionDepth > 0) {
fatalerror("UNIONs cannot contain code or data");
}
}
@@ -613,6 +615,10 @@ out_FindSection(char *pzName, ULONG secttype, SLONG org, SLONG bank, SLONG align
void
out_SetCurrentSection(struct Section * pSect)
{
if (nUnionDepth > 0) {
fatalerror("Cannot change the section within a UNION");
}
pCurrentSection = pSect;
nPC = pSect->nPC;
@@ -651,12 +657,11 @@ out_NewAlignedSection(char *pzName, ULONG secttype, SLONG alignment, SLONG bank)
}
/*
* Output an absolute byte
* Output an absolute byte (bypassing ROM/union checks)
*/
void
out_AbsByte(int b)
out_AbsByteBypassCheck(int b)
{
checkcodesection();
checksectionoverflow(1);
b &= 0xFF;
if (nPass == 2)
@@ -667,6 +672,16 @@ out_AbsByte(int b)
pPCSymbol->nValue += 1;
}
/*
* Output an absolute byte
*/
void
out_AbsByte(int b)
{
checkcodesection();
out_AbsByteBypassCheck(b);
}
void
out_AbsByteGroup(char *s, int length)
{
@@ -689,6 +704,9 @@ out_Skip(int skip)
pCurrentSection->nPC += skip;
nPC += skip;
pPCSymbol->nValue += skip;
} else if (nUnionDepth > 0) {
while (skip--)
out_AbsByteBypassCheck(CurrentOptions.fillchar);
} else {
checkcodesection();
while (skip--)