--- a/js/src/gc/Memory.cpp
+++ b/js/src/gc/Memory.cpp
@@ -9,16 +9,17 @@
 #include "mozilla/Atomics.h"
 #include "mozilla/TaggedAnonymousMemory.h"
 
 #include "js/HeapAPI.h"
 #include "vm/Runtime.h"
 
 #if defined(XP_WIN)
 
+#include "mozilla/Sprintf.h"
 #include "jswin.h"
 #include <psapi.h>
 
 #elif defined(SOLARIS)
 
 #include <sys/mman.h>
 #include <unistd.h>
 
@@ -848,17 +849,17 @@ void
 ProtectPages(void* p, size_t size)
 {
     MOZ_ASSERT(size % pageSize == 0);
     MOZ_RELEASE_ASSERT(size > 0);
     MOZ_RELEASE_ASSERT(p);
 #if defined(XP_WIN)
     DWORD oldProtect;
     if (!VirtualProtect(p, size, PAGE_NOACCESS, &oldProtect)) {
-        snprintf(sCrashReason, sizeof(sCrashReason),
+        SprintfLiteral(sCrashReason,
             "MOZ_CRASH(VirtualProtect(PAGE_NOACCESS) failed! Error code: %u)", GetLastError());
         MOZ_CRASH_ANNOTATE(sCrashReason);
         MOZ_REALLY_CRASH();
     }
     MOZ_ASSERT(oldProtect == PAGE_READWRITE);
 #else  // assume Unix
     if (mprotect(p, size, PROT_NONE))
         MOZ_CRASH("mprotect(PROT_NONE) failed");
@@ -869,17 +870,17 @@ void
 MakePagesReadOnly(void* p, size_t size)
 {
     MOZ_ASSERT(size % pageSize == 0);
     MOZ_RELEASE_ASSERT(size > 0);
     MOZ_RELEASE_ASSERT(p);
 #if defined(XP_WIN)
     DWORD oldProtect;
     if (!VirtualProtect(p, size, PAGE_READONLY, &oldProtect)) {
-        snprintf(sCrashReason, sizeof(sCrashReason),
+        SprintfLiteral(sCrashReason,
             "MOZ_CRASH(VirtualProtect(PAGE_READONLY) failed! Error code: %u)", GetLastError());
         MOZ_CRASH_ANNOTATE(sCrashReason);
         MOZ_REALLY_CRASH();
     }
     MOZ_ASSERT(oldProtect == PAGE_READWRITE);
 #else  // assume Unix
     if (mprotect(p, size, PROT_READ))
         MOZ_CRASH("mprotect(PROT_READ) failed");
@@ -890,17 +891,17 @@ void
 UnprotectPages(void* p, size_t size)
 {
     MOZ_ASSERT(size % pageSize == 0);
     MOZ_RELEASE_ASSERT(size > 0);
     MOZ_RELEASE_ASSERT(p);
 #if defined(XP_WIN)
     DWORD oldProtect;
     if (!VirtualProtect(p, size, PAGE_READWRITE, &oldProtect)) {
-        snprintf(sCrashReason, sizeof(sCrashReason),
+        SprintfLiteral(sCrashReason,
             "MOZ_CRASH(VirtualProtect(PAGE_READWRITE) failed! Error code: %u)", GetLastError());
         MOZ_CRASH_ANNOTATE(sCrashReason);
         MOZ_REALLY_CRASH();
     }
     MOZ_ASSERT(oldProtect == PAGE_NOACCESS || oldProtect == PAGE_READONLY);
 #else  // assume Unix
     if (mprotect(p, size, PROT_READ | PROT_WRITE))
         MOZ_CRASH("mprotect(PROT_READ | PROT_WRITE) failed");

--- a/mozglue/build/WindowsDllBlocklist.cpp
+++ b/mozglue/build/WindowsDllBlocklist.cpp
@@ -21,16 +21,17 @@
 #pragma warning( push )
 #pragma warning( disable : 4275 4530 ) // See msvc-stl-wrapper.template.h
 #include <map>
 #pragma warning( pop )
 
 #include "nsAutoPtr.h"
 
 #include "nsWindowsDllInterceptor.h"
+#include "mozilla/Sprintf.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WindowsVersion.h"
 #include "nsWindowsHelpers.h"
 #include "WindowsDllBlocklist.h"
 
 using namespace mozilla;
 
 #define ALL_VERSIONS   ((unsigned long long)-1LL)
@@ -255,18 +256,17 @@ static bool sUser32BeforeBlocklist;
 // Duplicated from xpcom glue. Ideally this should be shared.
 void
 printf_stderr(const char *fmt, ...)
 {
   if (IsDebuggerPresent()) {
     char buf[2048];
     va_list args;
     va_start(args, fmt);
-    vsnprintf(buf, sizeof(buf), fmt, args);
-    buf[sizeof(buf) - 1] = '\0';
+    VsprintfLiteral(buf, fmt, args);
     va_end(args);
     OutputDebugStringA(buf);
   }
 
   FILE *fp = _fdopen(_dup(2), "a");
   if (!fp)
       return;