handle negative zero; fixes #921

4 files changed, 72 insertions, 12 deletions

diff --git a/src/library.js b/src/library.js
index 793a78d7..382c21ad 100644
--- a/src/library.js
+++ b/src/library.js
@@ -2642,7 +2642,7 @@ LibraryManager.library = {
   //   format: A pointer to the format string.
   //   varargs: A pointer to the start of the arguments list.
   // Returns the resulting string string as a character array.
-  _formatString__deps: ['strlen'],
+  _formatString__deps: ['strlen', '_reallyNegative'],
   _formatString: function(format, varargs) {
     var textIndex = format;
     var argIndex = 0;
@@ -2897,7 +2897,6 @@ LibraryManager.library = {
             // Float.
             var currArg = getNextArg('double');
             var argText;
-
             if (isNaN(currArg)) {
               argText = 'nan';
               flagZeroPad = false;
@@ -2932,6 +2931,9 @@ LibraryManager.library = {
                 }
               } else if (next == {{{ charCode('f') }}} || next == {{{ charCode('F') }}}) {
                 argText = currArg.toFixed(effectivePrecision);
+                if (currArg === 0 && __reallyNegative(currArg)) {
+                  argText = '-' + argText;
+                }
               }
 
               var parts = argText.split('e');
@@ -5478,9 +5480,14 @@ LibraryManager.library = {
     return isNaN(x);
   },
   __isnan: 'isnan',
+
+  _reallyNegative: function(x) {
+    return x < 0 || (x === 0 && (1/x) === -Infinity);
+  },
+
+  copysign__deps: ['_reallyNegative'],
   copysign: function(a, b) {
-      if (a < 0 === b < 0) return a;
-      return -a;
+    return __reallyNegative(a) === __reallyNegative(b) ? a : -a;
   },
   copysignf: 'copysign',
   __signbit__deps: ['copysign'],
diff --git a/src/parseTools.js b/src/parseTools.js
index 2664baed..9fddacbb 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -818,7 +818,9 @@ function parseNumerical(value, type) {
     return '0';
   }
   if (isNumber(value)) {
-    return parseFloat(value).toString(); // will change e.g. 5.000000e+01 to 50
+    var ret = parseFloat(value); // will change e.g. 5.000000e+01 to 50
+    if (type in Runtime.FLOAT_TYPES && value[0] == '-' && ret === 0) return '-0'; // fix negative 0, toString makes it 0
+    return ret.toString();
   } else {
     return value;
   }
diff --git a/tests/runner.py b/tests/runner.py
index d375d2f7..fa90a01e 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -1234,6 +1234,59 @@ m_divisor is 1091269979
       '''
       self.do_run(src, ',0,,2,C!,0,C!,0,,65535,C!,0,')
 
+    def test_negative_zero(self):
+      src = r'''
+        #include <stdio.h>
+        #include <math.h>
+
+        int main() {
+          #define TEST(x, y) \
+            printf("%.2f, %.2f ==> %.2f\n", x, y, copysign(x, y));
+          TEST( 5.0f,  5.0f);
+          TEST( 5.0f, -5.0f);
+          TEST(-5.0f,  5.0f);
+          TEST(-5.0f, -5.0f);
+          TEST( 5.0f,  4.0f);
+          TEST( 5.0f, -4.0f);
+          TEST(-5.0f,  4.0f);
+          TEST(-5.0f, -4.0f);
+          TEST( 0.0f,  5.0f);
+          TEST( 0.0f, -5.0f);
+          TEST(-0.0f,  5.0f);
+          TEST(-0.0f, -5.0f);
+          TEST( 5.0f,  0.0f);
+          TEST( 5.0f, -0.0f);
+          TEST(-5.0f,  0.0f);
+          TEST(-5.0f, -0.0f);
+          TEST( 0.0f,  0.0f);
+          TEST( 0.0f, -0.0f);
+          TEST(-0.0f,  0.0f);
+          TEST(-0.0f, -0.0f);
+          return 0;
+        }
+      '''
+      self.do_run(src, '''5.00, 5.00 ==> 5.00
+5.00, -5.00 ==> -5.00
+-5.00, 5.00 ==> 5.00
+-5.00, -5.00 ==> -5.00
+5.00, 4.00 ==> 5.00
+5.00, -4.00 ==> -5.00
+-5.00, 4.00 ==> 5.00
+-5.00, -4.00 ==> -5.00
+0.00, 5.00 ==> 0.00
+0.00, -5.00 ==> -0.00
+-0.00, 5.00 ==> 0.00
+-0.00, -5.00 ==> -0.00
+5.00, 0.00 ==> 5.00
+5.00, -0.00 ==> -5.00
+-5.00, 0.00 ==> 5.00
+-5.00, -0.00 ==> -5.00
+0.00, 0.00 ==> 0.00
+0.00, -0.00 ==> -0.00
+-0.00, 0.00 ==> 0.00
+-0.00, -0.00 ==> -0.00
+''')
+
     def test_llvm_intrinsics(self):
       if self.emcc_args == None: return self.skip('needs ta2')
 
@@ -10005,6 +10058,7 @@ f.close()
         (path_from_root('tools', 'test-js-optimizer-asm-last.js'), open(path_from_root('tools', 'test-js-optimizer-asm-last-output.js')).read(),
          ['asm', 'last']),
       ]:
+        print input
         output = Popen(listify(NODE_JS) + [path_from_root('tools', 'js-optimizer.js'), input] + passes, stdin=PIPE, stdout=PIPE).communicate()[0]
         self.assertIdentical(expected, output.replace('\r\n', '\n').replace('\n\n', '\n'))
 
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 48ab5a1f..5ede0ce8 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -2287,19 +2287,16 @@ function minifyGlobals(ast) {
 function prepDotZero(ast) {
   traverse(ast, function(node, type) {
     if (type == 'unary-prefix' && node[1] == '+') {
-      if (node[2][0] == 'num') {
+      if (node[2][0] == 'num' ||
+          (node[2][0] == 'unary-prefix' && node[2][1] == '-' && node[2][2][0] == 'num')) {
         return ['call', ['name', 'DOT$ZERO'], [node[2]]];
-      } else if (node[2][0] == 'unary-prefix' && node[2][1] == '-' && node[2][2][0] == 'num') {
-        node[2][2][1] = -node[2][2][1];
-        return ['call', ['name', 'DOT$ZERO'], [node[2][2]]];
       }
     }
   });
 }
 function fixDotZero(js) {
-  return js.replace(/DOT\$ZERO\(((0x)?[-+]?[0-9a-f]*\.?[0-9]+([eE][-+]?[0-9]+)?)\)/g, function(m, num) {
-    if (num.substr(0, 2) == '0x') {
-      if (num[2] == '-') num = '-0x' + num.substr(3); // uglify generates 0x-8000 for some reason
+  return js.replace(/DOT\$ZERO\(([-+]?(0x)?[0-9a-f]*\.?[0-9]+([eE][-+]?[0-9]+)?)\)/g, function(m, num) {
+    if (num.substr(0, 2) == '0x' || num.substr(0, 3) == '-0x') {
       return eval(num) + '.0';
     }
     if (num.indexOf('.') >= 0) return num;