From d400e9491c0be93f34f368227d6a3e4d056d9061 Mon Sep 17 00:00:00 2001
From: Gaming4JC <g4jc@hyperbola.info>
Date: Sat, 8 Jun 2019 15:52:17 -0400
Subject: 1326454 - Make TokenStream::peekChar's signature fallible.

---
 js/src/frontend/TokenStream.cpp | 55 ++++++++++++++++++++++++++++++-----------
 js/src/frontend/TokenStream.h   |  8 +++---
 2 files changed, 45 insertions(+), 18 deletions(-)

(limited to 'js/src')

diff --git a/js/src/frontend/TokenStream.cpp b/js/src/frontend/TokenStream.cpp
index abb7228eb..6c5ea8fe9 100644
--- a/js/src/frontend/TokenStream.cpp
+++ b/js/src/frontend/TokenStream.cpp
@@ -968,7 +968,6 @@ TokenStream::getDirective(bool isMultiline, bool shouldWarnDeprecated,
 {
     MOZ_ASSERT(directiveLength <= 18);
     char16_t peeked[18];
-    int32_t c;
 
     if (peekChars(directiveLength, peeked) && CharsMatch(peeked, directive)) {
         if (shouldWarnDeprecated) {
@@ -979,18 +978,33 @@ TokenStream::getDirective(bool isMultiline, bool shouldWarnDeprecated,
         skipChars(directiveLength);
         tokenbuf.clear();
 
-        while ((c = peekChar()) && c != EOF && !unicode::IsSpaceOrBOM2(c)) {
-            getChar();
+        do {
+            int32_t c;
+            if (!peekChar(&c))
+                return false;
+
+            if (c == EOF || unicode::IsSpaceOrBOM2(c))
+                break;
+
+            consumeKnownChar(c);
+
             // Debugging directives can occur in both single- and multi-line
             // comments. If we're currently inside a multi-line comment, we also
             // need to recognize multi-line comment terminators.
-            if (isMultiline && c == '*' && peekChar() == '/') {
-                ungetChar('*');
-                break;
+            if (isMultiline && c == '*') {
+                int32_t c2;
+                if (!peekChar(&c2))
+                    return false;
+
+                if (c2 == '/') {
+                    ungetChar('*');
+                    break;
+                }
             }
+
             if (!tokenbuf.append(c))
                 return false;
-        }
+        } while (true);
 
         if (tokenbuf.empty()) {
             // The directive's URL was missing, but this is not quite an
@@ -1722,7 +1736,8 @@ TokenStream::getTokenInternal(TokenKind* ttp, Modifier modifier)
       case '/':
         // Look for a single-line comment.
         if (matchChar('/')) {
-            c = peekChar();
+            if (!peekChar(&c))
+                goto error;
             if (c == '@' || c == '#') {
                 bool shouldWarn = getChar() == '@';
                 if (!getDirectives(false, shouldWarn))
@@ -1789,7 +1804,8 @@ TokenStream::getTokenInternal(TokenKind* ttp, Modifier modifier)
             RegExpFlag reflags = NoFlags;
             unsigned length = tokenbuf.length() + 1;
             while (true) {
-                c = peekChar();
+                if (!peekChar(&c))
+                    goto error;
                 if (c == 'g' && !(reflags & GlobalFlag))
                     reflags = RegExpFlag(reflags | GlobalFlag);
                 else if (c == 'i' && !(reflags & IgnoreCaseFlag))
@@ -1806,7 +1822,8 @@ TokenStream::getTokenInternal(TokenKind* ttp, Modifier modifier)
                 length++;
             }
 
-            c = peekChar();
+            if (!peekChar(&c))
+                goto error;
             if (JS7_ISLET(c)) {
                 char buf[2] = { '\0', '\0' };
                 tp->pos.begin += length + 1;
@@ -1829,8 +1846,13 @@ TokenStream::getTokenInternal(TokenKind* ttp, Modifier modifier)
 
       case '-':
         if (matchChar('-')) {
-            if (peekChar() == '>' && !flags.isDirtyLine)
+            int32_t c2;
+            if (!peekChar(&c2))
+                goto error;
+
+            if (c2 == '>' && !flags.isDirtyLine)
                 goto skipline;
+
             tp->type = TOK_DEC;
         } else {
             tp->type = matchChar('=') ? TOK_SUBASSIGN : TOK_SUB;
@@ -1884,7 +1906,10 @@ TokenStream::getTokenInternal(TokenKind* ttp, Modifier modifier)
 bool
 TokenStream::matchBracedUnicode(bool* matched, uint32_t* cp)
 {
-    if (peekChar() != '{') {
+    int32_t c;
+    if (!peekChar(&c))
+        return false;
+    if (c != '{') {
         *matched = false;
         return true;
     }
@@ -2015,7 +2040,8 @@ TokenStream::getStringOrTemplateToken(int untilChar, Token** tp)
                 if (JS7_ISOCT(c)) {
                     int32_t val = JS7_UNOCT(c);
 
-                    c = peekChar();
+                    if (!peekChar(&c))
+                        return false;
 
                     // Strict mode code allows only \0, then a non-digit.
                     if (val != 0 || JS7_ISDEC(c)) {
@@ -2031,7 +2057,8 @@ TokenStream::getStringOrTemplateToken(int untilChar, Token** tp)
                     if (JS7_ISOCT(c)) {
                         val = 8 * val + JS7_UNOCT(c);
                         getChar();
-                        c = peekChar();
+                        if (!peekChar(&c))
+                            return false;
                         if (JS7_ISOCT(c)) {
                             int32_t save = val;
                             val = 8 * val + JS7_UNOCT(c);
diff --git a/js/src/frontend/TokenStream.h b/js/src/frontend/TokenStream.h
index 19385b499..e0e4b959e 100644
--- a/js/src/frontend/TokenStream.h
+++ b/js/src/frontend/TokenStream.h
@@ -990,10 +990,10 @@ class MOZ_STACK_CLASS TokenStream
         MOZ_ASSERT(c == expect);
     }
 
-    int32_t peekChar() {
-        int32_t c = getChar();
-        ungetChar(c);
-        return c;
+    MOZ_MUST_USE bool peekChar(int32_t* c) {
+        *c = getChar();
+        ungetChar(*c);
+        return true;
     }
 
     void skipChars(int n) {
-- 
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