diff --git a/xpcom/components/nsNativeComponentLoader.cpp b/xpcom/components/nsNativeComponentLoader.cpp
index 9f77af33af5e..3b3dac7c8d75 100644
--- a/xpcom/components/nsNativeComponentLoader.cpp
+++ b/xpcom/components/nsNativeComponentLoader.cpp
@@ -173,7 +173,7 @@ nsNativeModuleLoader::LoadModule(nsILocalFile* aFile, nsIModule* *aResult)
         fprintf(stderr,
                 "nsNativeModuleLoader::LoadModule(\"%s\") - load FAILED, "
                 "rv: %lx, error:\n\t%s\n",
-                filePath.get(), rv, errorMsg);
+                filePath.get(), (unsigned long)rv, errorMsg);
 #endif
 
         return rv;
diff --git a/xpcom/tests/TestCOMPtr.cpp b/xpcom/tests/TestCOMPtr.cpp
index e3e833b4f2d3..ca377ba27ead 100644
--- a/xpcom/tests/TestCOMPtr.cpp
+++ b/xpcom/tests/TestCOMPtr.cpp
@@ -368,7 +368,7 @@ main()
   {
     printf(">>main()\n");
 
-		printf("sizeof(nsCOMPtr<IFoo>) --> %d\n", sizeof(nsCOMPtr<IFoo>));
+		printf("sizeof(nsCOMPtr<IFoo>) --> %u\n", unsigned(sizeof(nsCOMPtr<IFoo>)));
 
 		TestBloat_Raw_Unsafe();
 		TestBloat_Smart();
diff --git a/xpcom/tests/TestHashtables.cpp b/xpcom/tests/TestHashtables.cpp
index 59c76819ac52..e4740e6c3b7d 100644
--- a/xpcom/tests/TestHashtables.cpp
+++ b/xpcom/tests/TestHashtables.cpp
@@ -93,7 +93,7 @@ EntityNode gEntities[] = {
   {"macr",175}
 };
 
-#define ENTITY_COUNT (sizeof(gEntities)/sizeof(EntityNode))
+#define ENTITY_COUNT (unsigned(sizeof(gEntities)/sizeof(EntityNode)))
 
 class EntityToUnicodeEntry : public PLDHashEntryHdr
 {
@@ -460,7 +460,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   PRUint32 i;
   for (i = 0; i < ENTITY_COUNT; ++i) {
@@ -527,7 +527,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   for (i = 0; i < ENTITY_COUNT; ++i) {
     printf("  Putting entry %u...", gEntities[i].mUnicode);
@@ -592,7 +592,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   for (i = 0; i < ENTITY_COUNT; ++i) {
     printf("  Putting entry %u...", gEntities[i].mUnicode);
@@ -661,7 +661,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   for (i = 0; i < ENTITY_COUNT; ++i) {
     printf("  Putting entry %u...", gEntities[i].mUnicode);
@@ -729,7 +729,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   nsCOMArray<IFoo> fooArray;
 
@@ -805,7 +805,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   for (i = 0; i < ENTITY_COUNT; ++i) {
     printf("  Putting entry %u...", gEntities[i].mUnicode);
@@ -879,7 +879,7 @@ main(void) {
   }
   printf("OK\n");
 
-  printf("Filling hash with %d entries.\n", ENTITY_COUNT);
+  printf("Filling hash with %u entries.\n", ENTITY_COUNT);
 
   for (i = 0; i < ENTITY_COUNT; ++i) {
     printf("  Putting entry %u...", gEntities[i].mUnicode);
diff --git a/xpcom/tests/TestRefPtr.cpp b/xpcom/tests/TestRefPtr.cpp
index 3f9504be1ff4..65a35559ad45 100644
--- a/xpcom/tests/TestRefPtr.cpp
+++ b/xpcom/tests/TestRefPtr.cpp
@@ -368,7 +368,7 @@ main()
   {
     printf(">>main()\n");
 
-		printf("sizeof(nsRefPtr<Foo>) --> %d\n", sizeof(nsRefPtr<Foo>));
+		printf("sizeof(nsRefPtr<Foo>) --> %u\n", unsigned(sizeof(nsRefPtr<Foo>)));
 
 		TestBloat_Raw_Unsafe();
 		TestBloat_Smart();
diff --git a/xpcom/typelib/xpt/tools/xpt_dump.c b/xpcom/typelib/xpt/tools/xpt_dump.c
index ebc2747c8089..da083114b928 100644
--- a/xpcom/typelib/xpt/tools/xpt_dump.c
+++ b/xpcom/typelib/xpt/tools/xpt_dump.c
@@ -227,7 +227,8 @@ main(int argc, char **argv)
     if (flen > 0) {
         size_t rv = fread(whole, 1, flen, in);
         if (rv < flen) {
-            fprintf(stderr, "short read (%d vs %d)! ouch!\n", rv, flen);
+            fprintf(stderr, "short read (%u vs %u)! ouch!\n",
+                    (unsigned int)rv, (unsigned int)flen);
             goto out;
         }
         if (ferror(in) != 0 || fclose(in) != 0)
diff --git a/xpcom/typelib/xpt/tools/xpt_link.c b/xpcom/typelib/xpt/tools/xpt_link.c
index c245d4a15095..76bb903ff301 100644
--- a/xpcom/typelib/xpt/tools/xpt_link.c
+++ b/xpcom/typelib/xpt/tools/xpt_link.c
@@ -236,7 +236,8 @@ main(int argc, char **argv)
         if (flen > 0) {
             size_t rv = fread(whole, 1, flen, in);
             if (rv < flen) {
-                fprintf(stderr, "short read (%d vs %d)! ouch!\n", rv, flen);
+                fprintf(stderr, "short read (%u vs %u)! ouch!\n",
+                        (unsigned int)rv, (unsigned int)flen);
                 return 1;
             }
             if (ferror(in) != 0 || fclose(in) != 0) {