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fix: prevent LTO from breaking settingGet/settingGetIndex round-trip #11577

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Merged
sensei-hacker merged 2 commits into from
May 22, 2026
+13 −3
Merged

fix: prevent LTO from breaking settingGet/settingGetIndex round-trip #11577

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4a937f4
fix: prevent LTO from breaking settingGet/settingGetIndex round-trip
sensei-hacker May 20, 2026
44c5934
fix: address code review issues in LTO noinline fix
sensei-hacker May 21, 2026
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16 changes: 13 additions & 3 deletions src/main/fc/settings.c
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Original file line number Diff line number Diff line change
Expand Up @@ -124,12 +124,20 @@ const setting_t *settingFind(const char *name)
return NULL;
}

const setting_t *settingGet(unsigned index)
// Under release builds (LTO enabled), inlining settingGet and settingGetIndex
// at their call sites in fc_msp.c produces wrong results for the
// settingGetIndex(ptr)->settingGet(index) round-trip, causing MSPV2_SETTING
// to return incorrect byte counts for some uint16_t settings.
// Use the raw attribute rather than NOINLINE because NOINLINE expands to
// nothing on non-F7/H7 targets (common.h:29), but LTO is enabled for all
// release targets and the bug affects all of them.
__attribute__((noinline)) const setting_t *settingGet(unsigned index)
{
return index < SETTINGS_TABLE_COUNT ? &settingsTable[index] : NULL;
}

unsigned settingGetIndex(const setting_t *val)
// noinline: same reason as settingGet above
__attribute__((noinline)) unsigned settingGetIndex(const setting_t *val)
{
return val - settingsTable;
}
Expand Down Expand Up @@ -215,7 +223,9 @@ size_t settingGetValueSize(const setting_t *val)
return 0; // Unreachable
}

pgn_t settingGetPgn(const setting_t *val)
// noinline: same reason as settingGet above; also does pointer arithmetic
// against settingsTable and is called from settingGetValuePointer.
__attribute__((noinline)) pgn_t settingGetPgn(const setting_t *val)
{
uint16_t pos = val - (const setting_t *)settingsTable;
uint16_t acc = 0;
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