Patch: handle broken backtrace()

[Jeff Sturm]

The backtrace() function on some glibc platforms (Linux/Alpha) is
apparently unimplemented and always returns zero.  This breaks
Throwable::fillInStackTrace, which always expect a return value
of at least one.

This patch fixes PR 286.

2000-07-19  Jeff Sturm  <jeff.sturm@appnet.com>

	* java/lang/natThrowable.cc (fillInStackTrace): Check for
	zero return from backtrace().

Index: java/lang/natThrowable.cc
===================================================================
RCS file: /cvs/java/libgcj/libjava/java/lang/natThrowable.cc,v
retrieving revision 1.6
diff -u -p -r1.6 natThrowable.cc
--- natThrowable.cc     2000/06/23 19:53:33     1.6
+++ natThrowable.cc     2000/07/19 13:41:19
@@ -61,9 +61,12 @@ java::lang::Throwable::fillInStackTrace 
   int n = backtrace (p, 128) - 1;  
 #endif
 
-  // ???  Might this cause a problem if the byte array isn't aligned?
-  stackTrace = JvNewByteArray (n * sizeof p[0]);
-  memcpy (elements (stackTrace), p+1, (n * sizeof p[0]));
+  if (n > 0)
+    {
+      // ???  Might this cause a problem if the byte array isn't aligned?
+      stackTrace = JvNewByteArray (n * sizeof p[0]);
+      memcpy (elements (stackTrace), p+1, (n * sizeof p[0]));
+    }
 
 #endif