From: qmuntal <quimmuntal@gmail.com>
Date: Fri, 19 Jan 2024 09:59:39 +0000 (+0100)
Subject: runtime: avoid loading winmm.dll on newer Windows versions
X-Git-Tag: go1.23rc1~1427
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=558919b45474bcdf191e9c9d8865699b036bc054;p=gostls13.git

runtime: avoid loading winmm.dll on newer Windows versions

winmm.dll is only used for timeBeginPeriod and timeEndPeriod, which are
not needed on Windows versions supporting high resolution timers, that
is Windows 10 version 1803, and later.

Updates #56745.

Change-Id: Ie9576638fb8d2b4e648283bec3170aefa76f9f82
Reviewed-on: https://go-review.googlesource.com/c/go/+/556935
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
---

diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index 6533b64004..cd0a3c260e 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -257,16 +257,6 @@ func loadOptionalSyscalls() {
 	_RtlGetCurrentPeb = windowsFindfunc(n32, []byte("RtlGetCurrentPeb\000"))
 	_RtlGetNtVersionNumbers = windowsFindfunc(n32, []byte("RtlGetNtVersionNumbers\000"))
 
-	m32 := windowsLoadSystemLib(winmmdll[:])
-	if m32 == 0 {
-		throw("winmm.dll not found")
-	}
-	_timeBeginPeriod = windowsFindfunc(m32, []byte("timeBeginPeriod\000"))
-	_timeEndPeriod = windowsFindfunc(m32, []byte("timeEndPeriod\000"))
-	if _timeBeginPeriod == nil || _timeEndPeriod == nil {
-		throw("timeBegin/EndPeriod not found")
-	}
-
 	ws232 := windowsLoadSystemLib(ws2_32dll[:])
 	if ws232 == 0 {
 		throw("ws2_32.dll not found")
@@ -421,6 +411,21 @@ func initHighResTimer() {
 	if h != 0 {
 		haveHighResTimer = true
 		stdcall1(_CloseHandle, h)
+	} else {
+		// Only load winmm.dll if we need it.
+		// This avoids a dependency on winmm.dll for Go programs
+		// that run on new Windows versions.
+		m32 := windowsLoadSystemLib(winmmdll[:])
+		if m32 == 0 {
+			print("runtime: LoadLibraryExW failed; errno=", getlasterror(), "\n")
+			throw("winmm.dll not found")
+		}
+		_timeBeginPeriod = windowsFindfunc(m32, []byte("timeBeginPeriod\000"))
+		_timeEndPeriod = windowsFindfunc(m32, []byte("timeEndPeriod\000"))
+		if _timeBeginPeriod == nil || _timeEndPeriod == nil {
+			print("runtime: GetProcAddress failed; errno=", getlasterror(), "\n")
+			throw("timeBegin/EndPeriod not found")
+		}
 	}
 }