1 files changed, 20 insertions, 0 deletions
diff --git a/exp-sgcheck/tests/tricky.c b/exp-sgcheck/tests/tricky.c
new file mode 100644
index 00000000..624f9e4a
--- /dev/null
+++ b/exp-sgcheck/tests/tricky.c
@@ -0,0 +1,20 @@
+
+#include <stdlib.h>
+
+int main(void)
+{
+   // When I had n-u --> u, this gave a false positive... can happen because
+   // p+up can give n if you are (un)lucky, because the result is close enough
+   // to zero.
+   int  u[20];
+   int* p = malloc(sizeof(int) * 100);
+   int* n;
+   int* x;
+   
+   p[0] = 0;                           // ok
+   n = (int*)((long)p + (long)u);      // result is n, because near zero!
+   x = (int*)((long)n - (long)u);      // x == p
+   x[0] = 0;                           // ok, originally caused false pos.
+
+   return 0;
+}