From 24404d9047160577e82f71825ee85d988c0c5113 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Wed, 25 Feb 2026 10:21:20 -0800
Subject: [PATCH] Fixed timer overflow on some platforms
We have an implementation that uses 128-bit math and one that handles large values without it (thanks @jessechounard and @rabbit-ecl!)
Fixes https://github.com/libsdl-org/SDL/issues/15042
---
src/timer/SDL_timer.c | 34 ++++++++++++++++++++++++++++------
1 file changed, 28 insertions(+), 6 deletions(-)
diff --git a/src/timer/SDL_timer.c b/src/timer/SDL_timer.c
index ebc864871306c..9bd3da408f140 100644
--- a/src/timer/SDL_timer.c
+++ b/src/timer/SDL_timer.c
@@ -535,11 +535,20 @@ bool SDL_RemoveTimer(SDL_TimerID id)
#endif // !SDL_PLATFORM_EMSCRIPTEN
+#ifdef USE_128BIT_MATH
+typedef unsigned __int128 Uint128;
+#endif
+
static Uint64 tick_start;
+#ifdef USE_128BIT_MATH
+static Uint128 tick_numerator_ns;
+static Uint128 tick_numerator_ms;
+#else
static Uint32 tick_numerator_ns;
static Uint32 tick_denominator_ns;
static Uint32 tick_numerator_ms;
static Uint32 tick_denominator_ms;
+#endif
#if defined(SDL_TIMER_WINDOWS) && !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
#include <mmsystem.h>
@@ -583,7 +592,9 @@ static void SDLCALL SDL_TimerResolutionChanged(void *userdata, const char *name,
void SDL_InitTicks(void)
{
Uint64 tick_freq;
+#ifndef USE_128BIT_MATH
Uint32 gcd;
+#endif
if (tick_start) {
return;
@@ -597,6 +608,10 @@ void SDL_InitTicks(void)
tick_freq = SDL_GetPerformanceFrequency();
SDL_assert(tick_freq > 0 && tick_freq <= (Uint64)SDL_MAX_UINT32);
+#ifdef USE_128BIT_MATH
+ tick_numerator_ns = ((Uint128)SDL_NS_PER_SECOND << 32) / tick_freq;
+ tick_numerator_ms = ((Uint128)SDL_MS_PER_SECOND << 32) / tick_freq;
+#else
gcd = SDL_CalculateGCD(SDL_NS_PER_SECOND, (Uint32)tick_freq);
tick_numerator_ns = (SDL_NS_PER_SECOND / gcd);
tick_denominator_ns = (Uint32)(tick_freq / gcd);
@@ -604,6 +619,7 @@ void SDL_InitTicks(void)
gcd = SDL_CalculateGCD(SDL_MS_PER_SECOND, (Uint32)tick_freq);
tick_numerator_ms = (SDL_MS_PER_SECOND / gcd);
tick_denominator_ms = (Uint32)(tick_freq / gcd);
+#endif
tick_start = SDL_GetPerformanceCounter();
if (!tick_start) {
@@ -630,9 +646,12 @@ Uint64 SDL_GetTicksNS(void)
}
starting_value = (SDL_GetPerformanceCounter() - tick_start);
- value = (starting_value * tick_numerator_ns);
- SDL_assert(value >= starting_value);
- value /= tick_denominator_ns;
+#ifdef USE_128BIT_MATH
+ value = (Uint64)(((Uint128)starting_value * tick_numerator_ns) >> 32);
+#else
+ value = (starting_value / tick_denominator_ns) * tick_numerator_ns +
+ (starting_value % tick_denominator_ns) * tick_numerator_ns / tick_denominator_ns;
+#endif
return value;
}
@@ -645,9 +664,12 @@ Uint64 SDL_GetTicks(void)
}
starting_value = (SDL_GetPerformanceCounter() - tick_start);
- value = (starting_value * tick_numerator_ms);
- SDL_assert(value >= starting_value);
- value /= tick_denominator_ms;
+#ifdef USE_128BIT_MATH
+ value = (Uint64)(((Uint128)starting_value * tick_numerator_ms) >> 32);
+#else
+ value = (starting_value / tick_denominator_ms) * tick_numerator_ms +
+ (starting_value % tick_denominator_ms) * tick_numerator_ms / tick_denominator_ms;
+#endif
return value;
}