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Handle -Wtruncation for link-time jr values

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Fixes #2028
This commit is contained in:
Rangi
2026-07-21 14:51:58 -04:00
parent 50678d0942
commit ec5e6cbabb
7 changed files with 24 additions and 3 deletions
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src/link/patch.cpp
+6 -3
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@@ -585,12 +585,15 @@ static void applyFilePatches(Section &section, Section &dataSection) {
rpnErrorAt(patch, "PC has no value outside of a section");
dataSection.data[offset] = 0;
} else {
// A `jr` is *encoded* in ROM as a 1-byte (8-bit) offset, so here `typeSize == 8`,
// but the object's *value* size is a 16-bit absolute address, so we pass 16 here.
checkPatchSize(patch, value, 16);
// Offset is relative to the byte *after* the operand
// PC as operand to `jr` is lower than reference PC by 2
uint16_t address = patch.pcSection->org + patch.pcOffset + 2;
// The truncation of `value - address` is intentional, since
// a low ROM0 address may `jr` to a high HRAM one.
int16_t jumpOffset = value - address;
// The 16-bit truncation of `value - address` is intentional, since
// a low ROM0 address may `jr` backwards to a high HRAM one.
int16_t jumpOffset = static_cast<int16_t>(value - address);
if (jumpOffset < -128 || jumpOffset > 127) {
firstErrorAt(