diff --git a/js/src/jsprf.cpp b/js/src/jsprf.cpp
index 72bab422061..42580fedf5e 100644
--- a/js/src/jsprf.cpp
+++ b/js/src/jsprf.cpp
@@ -40,7 +40,7 @@ using namespace js;
 
 struct SprintfState
 {
-    int (*stuff)(SprintfState *ss, const char *sp, size_t len);
+    bool (*stuff)(SprintfState *ss, const char *sp, size_t len);
 
     char *base;
     char *cur;
@@ -82,19 +82,18 @@ typedef mozilla::Vector<NumArgState, 20, js::SystemAllocPolicy> NumArgStateVecto
 #define FLAG_ZEROS      0x8
 #define FLAG_NEG        0x10
 
-inline int
+inline bool
 generic_write(SprintfState *ss, const char *src, size_t srclen)
 {
     return (*ss->stuff)(ss, src, srclen);
 }
 
-inline int
+inline bool
 generic_write(SprintfState *ss, const char16_t *src, size_t srclen)
 {
     const size_t CHUNK_SIZE = 64;
     char chunk[CHUNK_SIZE];
 
-    int rv = 0;
     size_t j = 0;
     size_t i = 0;
     while (i < srclen) {
@@ -102,53 +101,48 @@ generic_write(SprintfState *ss, const char16_t *src, size_t srclen)
         chunk[j++] = char(src[i++]);
 
         if (j == CHUNK_SIZE || i == srclen) {
-            rv = (*ss->stuff)(ss, chunk, j);
-            if (rv != 0)
-                return rv;
+            if (!(*ss->stuff)(ss, chunk, j))
+                return false;
             j = 0;
         }
     }
-    return 0;
+    return true;
 }
 
 // Fill into the buffer using the data in src
 template <typename Char>
-static int
+static bool
 fill2(SprintfState *ss, const Char *src, int srclen, int width, int flags)
 {
     char space = ' ';
-    int rv;
 
     width -= srclen;
     if (width > 0 && (flags & FLAG_LEFT) == 0) {    // Right adjusting
         if (flags & FLAG_ZEROS)
             space = '0';
         while (--width >= 0) {
-            rv = (*ss->stuff)(ss, &space, 1);
-            if (rv < 0)
-                return rv;
+            if (!(*ss->stuff)(ss, &space, 1))
+                return false;
         }
     }
 
     // Copy out the source data
-    rv = generic_write(ss, src, srclen);
-    if (rv < 0)
-        return rv;
+    if (!generic_write(ss, src, srclen))
+        return false;
 
     if (width > 0 && (flags & FLAG_LEFT) != 0) {    // Left adjusting
         while (--width >= 0) {
-            rv = (*ss->stuff)(ss, &space, 1);
-            if (rv < 0)
-                return rv;
+            if (!(*ss->stuff)(ss, &space, 1))
+                return false;
         }
     }
-    return 0;
+    return true;
 }
 
 /*
  * Fill a number. The order is: optional-sign zero-filling conversion-digits
  */
-static int
+static bool
 fill_n(SprintfState *ss, const char *src, int srclen, int width, int prec, int type, int flags)
 {
     int zerowidth = 0;
@@ -157,7 +151,6 @@ fill_n(SprintfState *ss, const char *src, int srclen, int width, int prec, int t
     int leftspaces = 0;
     int rightspaces = 0;
     int cvtwidth;
-    int rv;
     char sign;
 
     if ((type & 1) == 0) {
@@ -200,54 +193,41 @@ fill_n(SprintfState *ss, const char *src, int srclen, int width, int prec, int t
         }
     }
     while (--leftspaces >= 0) {
-        rv = (*ss->stuff)(ss, " ", 1);
-        if (rv < 0) {
-            return rv;
-        }
+        if (!(*ss->stuff)(ss, " ", 1))
+            return false;
     }
     if (signwidth) {
-        rv = (*ss->stuff)(ss, &sign, 1);
-        if (rv < 0) {
-            return rv;
-        }
+        if (!(*ss->stuff)(ss, &sign, 1))
+            return false;
     }
     while (--precwidth >= 0) {
-        rv = (*ss->stuff)(ss, "0", 1);
-        if (rv < 0) {
-            return rv;
-        }
+        if (!(*ss->stuff)(ss, "0", 1))
+            return false;
     }
     while (--zerowidth >= 0) {
-        rv = (*ss->stuff)(ss, "0", 1);
-        if (rv < 0) {
-            return rv;
-        }
-    }
-    rv = (*ss->stuff)(ss, src, uint32_t(srclen));
-    if (rv < 0) {
-        return rv;
+        if (!(*ss->stuff)(ss, "0", 1))
+            return false;
     }
+    if (!(*ss->stuff)(ss, src, uint32_t(srclen)))
+        return false;
     while (--rightspaces >= 0) {
-        rv = (*ss->stuff)(ss, " ", 1);
-        if (rv < 0) {
-            return rv;
-        }
+        if (!(*ss->stuff)(ss, " ", 1))
+            return false;
     }
-    return 0;
+    return true;
 }
 
 /* Convert a long into its printable form. */
-static int cvt_l(SprintfState *ss, long num, int width, int prec, int radix,
-                 int type, int flags, const char *hexp)
+static bool cvt_l(SprintfState *ss, long num, int width, int prec, int radix,
+                  int type, int flags, const char *hexp)
 {
     char cvtbuf[100];
     char *cvt;
     int digits;
 
     // according to the man page this needs to happen
-    if ((prec == 0) && (num == 0)) {
-        return 0;
-    }
+    if ((prec == 0) && (num == 0))
+        return true;
 
     // Converting decimal is a little tricky. In the unsigned case we
     // need to stop when we hit 10 digits. In the signed case, we can
@@ -271,12 +251,12 @@ static int cvt_l(SprintfState *ss, long num, int width, int prec, int radix,
 }
 
 /* Convert a 64-bit integer into its printable form. */
-static int cvt_ll(SprintfState *ss, int64_t num, int width, int prec, int radix,
-                  int type, int flags, const char *hexp)
+static bool cvt_ll(SprintfState *ss, int64_t num, int width, int prec, int radix,
+                   int type, int flags, const char *hexp)
 {
     // According to the man page, this needs to happen.
     if (prec == 0 && num == 0)
-        return 0;
+        return true;
 
     // Converting decimal is a little tricky. In the unsigned case we
     // need to stop when we hit 10 digits. In the signed case, we can
@@ -309,7 +289,7 @@ static int cvt_ll(SprintfState *ss, int64_t num, int width, int prec, int radix,
  *
  * XXX stop using sprintf to convert floating point
  */
-static int cvt_f(SprintfState *ss, double d, const char *fmt0, const char *fmt1)
+static bool cvt_f(SprintfState *ss, double d, const char *fmt0, const char *fmt1)
 {
     char fin[20];
     char fout[300];
@@ -318,7 +298,7 @@ static int cvt_f(SprintfState *ss, double d, const char *fmt0, const char *fmt1)
     MOZ_ASSERT((amount > 0) && (amount < (int)sizeof(fin)));
     if (amount >= (int)sizeof(fin)) {
         // Totally bogus % command to sprintf. Just ignore it
-        return 0;
+        return true;
     }
     js_memcpy(fin, fmt0, (size_t)amount);
     fin[amount] = 0;
@@ -355,11 +335,11 @@ static inline size_t generic_strlen(const char16_t *s) { return js_strlen(s); }
  * where -1 means until NUL.
  */
 template <typename Char>
-static int
+static bool
 cvt_s(SprintfState *ss, const Char *s, int width, int prec, int flags)
 {
     if (prec == 0)
-        return 0;
+        return true;
     if (!s)
         s = generic_null_str(s);
 
@@ -590,7 +570,7 @@ BuildArgArray(const char *fmt, va_list ap, NumArgStateVector& nas)
 /*
  * The workhorse sprintf code.
  */
-static int
+static bool
 dosprintf(SprintfState *ss, const char *fmt, va_list ap)
 {
     char c;
@@ -610,7 +590,7 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
     static const char hex[] = "0123456789abcdef";
     static const char HEX[] = "0123456789ABCDEF";
     const char *hexp;
-    int rv, i;
+    int i;
     char pattern[20];
     const char *dolPt = nullptr;  // in "%4$.2f", dolPt will point to '.'
 
@@ -621,15 +601,14 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
     if (!BuildArgArray(fmt, ap, nas)) {
         // the fmt contains error Numbered Argument format, jliu@netscape.com
         MOZ_ASSERT(0);
-        return rv;
+        return false;
     }
 
     while ((c = *fmt++) != 0) {
         if (c != '%') {
-            rv = (*ss->stuff)(ss, fmt - 1, 1);
-            if (rv < 0) {
-                return rv;
-            }
+            if (!(*ss->stuff)(ss, fmt - 1, 1))
+                return false;
+
             continue;
         }
         fmt0 = fmt - 1;
@@ -640,10 +619,9 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
         c = *fmt++;
         if (c == '%') {
             // quoting a % with %%
-            rv = (*ss->stuff)(ss, fmt - 1, 1);
-            if (rv < 0) {
-                return rv;
-            }
+            if (!(*ss->stuff)(ss, fmt - 1, 1))
+                return false;
+
             continue;
         }
 
@@ -656,7 +634,7 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
             }
 
             if (nas[i - 1].type == TYPE_UNKNOWN)
-                return -1;
+                return false;
 
             ap = nas[i - 1].ap;
             dolPt = fmt;
@@ -785,10 +763,9 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
               case TYPE_UINT32:
                 u.l = (long)va_arg(ap, uint32_t);
               do_long:
-                rv = cvt_l(ss, u.l, width, prec, radix, type, flags, hexp);
-                if (rv < 0) {
-                    return rv;
-                }
+                if (!cvt_l(ss, u.l, width, prec, radix, type, flags, hexp))
+                    return false;
+
                 break;
 
               case TYPE_INT64:
@@ -801,10 +778,9 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
               case TYPE_UINT64:
                 u.ll = va_arg(ap, uint64_t);
               do_longlong:
-                rv = cvt_ll(ss, u.ll, width, prec, radix, type, flags, hexp);
-                if (rv < 0) {
-                    return rv;
-                }
+                if (!cvt_ll(ss, u.ll, width, prec, radix, type, flags, hexp))
+                    return false;
+
                 break;
             }
             break;
@@ -819,41 +795,35 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
                 if (i < int(sizeof(pattern))) {
                     pattern[0] = '%';
                     js_memcpy(&pattern[1], dolPt, size_t(i));
-                    rv = cvt_f(ss, u.d, pattern, &pattern[i + 1]);
+                    if (!cvt_f(ss, u.d, pattern, &pattern[i + 1]))
+                        return false;
                 }
-            } else
-                rv = cvt_f(ss, u.d, fmt0, fmt);
-
-            if (rv < 0) {
-                return rv;
+            } else {
+                if (!cvt_f(ss, u.d, fmt0, fmt))
+                    return false;
             }
+
             break;
 
           case 'c':
             if ((flags & FLAG_LEFT) == 0) {
                 while (width-- > 1) {
-                    rv = (*ss->stuff)(ss, " ", 1);
-                    if (rv < 0) {
-                        return rv;
-                    }
+                    if (!(*ss->stuff)(ss, " ", 1))
+                        return false;
                 }
             }
             switch (type) {
               case TYPE_INT16:
               case TYPE_INTN:
                 u.ch = va_arg(ap, int);
-                rv = (*ss->stuff)(ss, &u.ch, 1);
+                if (!(*ss->stuff)(ss, &u.ch, 1))
+                    return false;
                 break;
             }
-            if (rv < 0) {
-                return rv;
-            }
             if (flags & FLAG_LEFT) {
                 while (width-- > 1) {
-                    rv = (*ss->stuff)(ss, " ", 1);
-                    if (rv < 0) {
-                        return rv;
-                    }
+                    if (!(*ss->stuff)(ss, " ", 1))
+                        return false;
                 }
             }
             break;
@@ -885,13 +855,12 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
           case 's':
             if(type == TYPE_INT16) {
                 u.ws = va_arg(ap, const char16_t*);
-                rv = cvt_s(ss, u.ws, width, prec, flags);
+                if (!cvt_s(ss, u.ws, width, prec, flags))
+                    return false;
             } else {
                 u.s = va_arg(ap, const char*);
-                rv = cvt_s(ss, u.s, width, prec, flags);
-            }
-            if (rv < 0) {
-                return rv;
+                if (!cvt_s(ss, u.s, width, prec, flags))
+                    return false;
             }
             break;
 
@@ -907,21 +876,18 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
 #if 0
             MOZ_ASSERT(0);
 #endif
-            rv = (*ss->stuff)(ss, "%", 1);
-            if (rv < 0) {
-                return rv;
-            }
-            rv = (*ss->stuff)(ss, fmt - 1, 1);
-            if (rv < 0) {
-                return rv;
-            }
+            if (!(*ss->stuff)(ss, "%", 1))
+                return false;
+            if (!(*ss->stuff)(ss, fmt - 1, 1))
+                return false;
         }
     }
 
     // Stuff trailing NUL
-    rv = (*ss->stuff)(ss, "\0", 1);
+    if (!(*ss->stuff)(ss, "\0", 1))
+        return false;
 
-    return rv;
+    return true;
 }
 
 /************************************************************************/
@@ -930,7 +896,7 @@ dosprintf(SprintfState *ss, const char *fmt, va_list ap)
  * Stuff routine that automatically grows the js_malloc'd output buffer
  * before it overflows.
  */
-static int
+static bool
 GrowStuff(SprintfState *ss, const char *sp, size_t len)
 {
     ptrdiff_t off;
@@ -944,7 +910,7 @@ GrowStuff(SprintfState *ss, const char *sp, size_t len)
         newbase = static_cast<char *>(js_realloc(ss->base, newlen));
         if (!newbase) {
             /* Ran out of memory */
-            return -1;
+            return false;
         }
         ss->base = newbase;
         ss->maxlen = newlen;
@@ -957,7 +923,7 @@ GrowStuff(SprintfState *ss, const char *sp, size_t len)
         *ss->cur++ = *sp++;
     }
     MOZ_ASSERT(size_t(ss->cur - ss->base) <= ss->maxlen);
-    return 0;
+    return true;
 }
 
 /*
@@ -988,14 +954,12 @@ JS_PUBLIC_API(char *)
 JS_vsmprintf(const char *fmt, va_list ap)
 {
     SprintfState ss;
-    int rv;
 
     ss.stuff = GrowStuff;
     ss.base = 0;
     ss.cur = 0;
     ss.maxlen = 0;
-    rv = dosprintf(&ss, fmt, ap);
-    if (rv < 0) {
+    if (!dosprintf(&ss, fmt, ap)) {
         js_free(ss.base);
         return 0;
     }
@@ -1005,7 +969,7 @@ JS_vsmprintf(const char *fmt, va_list ap)
 /*
  * Stuff routine that discards overflow data
  */
-static int
+static bool
 LimitStuff(SprintfState *ss, const char *sp, size_t len)
 {
     size_t limit = ss->maxlen - (ss->cur - ss->base);
@@ -1016,7 +980,7 @@ LimitStuff(SprintfState *ss, const char *sp, size_t len)
         --len;
         *ss->cur++ = *sp++;
     }
-    return 0;
+    return true;
 }
 
 /*
@@ -1046,9 +1010,8 @@ JS_vsnprintf(char *out, uint32_t outlen, const char *fmt, va_list ap)
     uint32_t n;
 
     MOZ_ASSERT(int32_t(outlen) > 0);
-    if (int32_t(outlen) <= 0) {
+    if (int32_t(outlen) <= 0)
         return 0;
-    }
 
     ss.stuff = LimitStuff;
     ss.base = out;
@@ -1080,7 +1043,6 @@ JS_PUBLIC_API(char *)
 JS_vsprintf_append(char *last, const char *fmt, va_list ap)
 {
     SprintfState ss;
-    int rv;
 
     ss.stuff = GrowStuff;
     if (last) {
@@ -1093,8 +1055,7 @@ JS_vsprintf_append(char *last, const char *fmt, va_list ap)
         ss.cur = 0;
         ss.maxlen = 0;
     }
-    rv = dosprintf(&ss, fmt, ap);
-    if (rv < 0) {
+    if (!dosprintf(&ss, fmt, ap)) {
         js_free(ss.base);
         return 0;
     }