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Handle QueryPerformanceCounter failure with fallback #694

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Handle QueryPerformanceCounter failure with fallback #694

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37 changes: 34 additions & 3 deletions src/windows/system.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1438,11 +1438,42 @@ bool Sys_IsMainThread(void)
return GetCurrentThreadId() == main_thread_id;
}

/*
=============
Sys_Milliseconds

Returns milliseconds since startup using a monotonic clock.
Falls back to a lower-resolution timer if high-resolution queries fail.
=============
*/
unsigned Sys_Milliseconds(void)
{
LARGE_INTEGER tm;
QueryPerformanceCounter(&tm);
return tm.QuadPart * 1000ULL / timer_freq.QuadPart;
static bool qpc_available = true;
static DWORD fallback_base = 0;
static unsigned last_msec = 0;

if (qpc_available) {
LARGE_INTEGER tm;
if (QueryPerformanceCounter(&tm)) {
unsigned msec = static_cast<unsigned>(tm.QuadPart * 1000ULL / timer_freq.QuadPart);
if (msec < last_msec)
msec = last_msec;
last_msec = msec;
return msec;
}

Sys_Printf("QueryPerformanceCounter failed; falling back to timeGetTime (low resolution).\n");
qpc_available = false;
fallback_base = timeGetTime();
}

DWORD current = timeGetTime();
unsigned msec = current - fallback_base;
if (msec < last_msec)
Comment on lines +1465 to +1472
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@chatgpt-codex-connector chatgpt-codex-connector bot Nov 21, 2025

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P1 Badge Fallback timer never advances after QPC failure

When QueryPerformanceCounter fails, fallback_base is set to the current timeGetTime() while last_msec still holds the absolute QPC-derived milliseconds since boot. The very next call computes msec = current - fallback_base (near zero) and clamps it to last_msec, but fallback_base is not offset by that value. The result is that Sys_Milliseconds returns a constant last_msec until timeGetTime() has advanced by at least that many milliseconds—potentially freezing the timer for many minutes or hours after the fallback is triggered. Consider seeding fallback_base so timeGetTime() continues from last_msec immediately.

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msec = last_msec;
else
last_msec = msec;
return msec;
}

void Sys_AddDefaultConfig(void)
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