[PATCH 1/1] ddraw/tests: Fix overflow bugs in compare_float.

[Jeff Smith]

From: Jeff Smith

1. Subtracting integers may result in an overflow or underflow.
2. Right at the 'edge' of underflowing, the result of subtraction may be
   INT_MIN, and the call to abs() will also result in INT_MIN.

This fix accounts for all of these conditions.
---
 dlls/ddraw/tests/ddraw1.c | 9 ++++++++-
 dlls/ddraw/tests/ddraw2.c | 9 ++++++++-
 dlls/ddraw/tests/ddraw4.c | 9 ++++++++-
 dlls/ddraw/tests/ddraw7.c | 9 ++++++++-
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/dlls/ddraw/tests/ddraw1.c b/dlls/ddraw/tests/ddraw1.c
index cde80c58e99..48ce8214180 100644
--- a/dlls/ddraw/tests/ddraw1.c
+++ b/dlls/ddraw/tests/ddraw1.c
@@ -54,13 +54,20 @@ static BOOL compare_float(float f, float g, unsigned int ulps)
 {
     int x = *(int *)&f;
     int y = *(int *)&g;
+    int delta;

if (x < 0)
         x = INT_MIN - x;
     if (y < 0)
         y = INT_MIN - y;

-    if (abs(x - y) > ulps)
+    delta = x - y;
+
+    /* Check for overflow and related conditions */
+    if (((x ^ y) & (x ^ delta)) < 0 || delta == INT_MIN)
+        return FALSE;
+
+    if (abs(delta) > ulps)
         return FALSE;

return TRUE;
diff --git a/dlls/ddraw/tests/ddraw2.c b/dlls/ddraw/tests/ddraw2.c
index 86056014f96..0b226c97d3e 100644
--- a/dlls/ddraw/tests/ddraw2.c
+++ b/dlls/ddraw/tests/ddraw2.c
@@ -55,13 +55,20 @@ static BOOL compare_float(float f, float g, unsigned int ulps)
 {
     int x = *(int *)&f;
     int y = *(int *)&g;
+    int delta;

if (x < 0)
         x = INT_MIN - x;
     if (y < 0)
         y = INT_MIN - y;

-    if (abs(x - y) > ulps)
+    delta = x - y;
+
+    /* Check for overflow and related conditions */
+    if (((x ^ y) & (x ^ delta)) < 0 || delta == INT_MIN)
+        return FALSE;
+
+    if (abs(delta) > ulps)
         return FALSE;

return TRUE;
diff --git a/dlls/ddraw/tests/ddraw4.c b/dlls/ddraw/tests/ddraw4.c
index 4458cea5145..93ad8636a17 100644
--- a/dlls/ddraw/tests/ddraw4.c
+++ b/dlls/ddraw/tests/ddraw4.c
@@ -61,13 +61,20 @@ static BOOL compare_float(float f, float g, unsigned int ulps)
 {
     int x = *(int *)&f;
     int y = *(int *)&g;
+    int delta;

if (x < 0)
         x = INT_MIN - x;
     if (y < 0)
         y = INT_MIN - y;

-    if (abs(x - y) > ulps)
+    delta = x - y;
+
+    /* Check for overflow and related conditions */
+    if (((x ^ y) & (x ^ delta)) < 0 || delta == INT_MIN)
+        return FALSE;
+
+    if (abs(delta) > ulps)
         return FALSE;

return TRUE;
diff --git a/dlls/ddraw/tests/ddraw7.c b/dlls/ddraw/tests/ddraw7.c
index bbb78169aea..b3a0a60af87 100644
--- a/dlls/ddraw/tests/ddraw7.c
+++ b/dlls/ddraw/tests/ddraw7.c
@@ -72,13 +72,20 @@ static BOOL compare_float(float f, float g, unsigned int ulps)
 {
     int x = *(int *)&f;
     int y = *(int *)&g;
+    int delta;

if (x < 0)
         x = INT_MIN - x;
     if (y < 0)
         y = INT_MIN - y;

-    if (abs(x - y) > ulps)
+    delta = x - y;
+
+    /* Check for overflow and related conditions */
+    if (((x ^ y) & (x ^ delta)) < 0 || delta == INT_MIN)
+        return FALSE;
+
+    if (abs(delta) > ulps)
         return FALSE;

return TRUE;