[PATCH] PPC sim: Don't close file descriptors 0, 1, or 2

[Kevin Buettner <kevinb@redhat.com>]

In my testing, this patch eliminates all of the "unresolved testcases"
when testing GDB against the powerpc simulator.

E.g. for gdb.base.exp, I see this in the log file:

    (gdb) next
    66	    return (value); /* set breakpoint 19 here */
    (gdb) PASS: gdb.base/break.exp: next over recursive call
    backtrace
    #0  factorial (value=120) at testsuite/gdb.base/break.c:66
    #1  0x10000428 in factorial (value=6) at testsuite/gdb.base/break.c:64
    #2  0x10000370 in main (argc=1, argv=0xdfffee20, envp=0xdfffee28) at testsuite/gdb.base/break.c:47
    (gdb) PASS: gdb.base/break.exp: backtrace from factorial(5.1)
    continue
    Continuing.
    720
    ERROR: Process no longer exists
    UNRESOLVED: gdb.base/break.exp: continue until exit at recursive next test

With this patch/change in place, this bit of the test runs as expected:

    (gdb) next
    66	    return (value); /* set breakpoint 19 here */
    (gdb) PASS: gdb.base/break.exp: next over recursive call
    backtrace
    #0  factorial (value=120) at testsuite/gdb.base/break.c:66
    #1  0x10000428 in factorial (value=6) at testsuite/gdb.base/break.c:64
    #2  0x10000370 in main (argc=1, argv=0xdfffee20, envp=0xdfffee28) at testsuite/gdb.base/break.c:47
    (gdb) PASS: gdb.base/break.exp: backtrace from factorial(5.1)
    continue
    Continuing.
    720
    [Inferior 1 (process 42000) exited normally]

This occurs because the powerpc simulator closes, on behalf of the
testcase, the file descriptors associated with stdin, stdout, and
stderr.  GDB still needs these descriptors to communicate with the
user or, in this case, with the testing framework.

sim/ppc/ChangeLog:
    
    	* emul_netbsd.c (do_close): Don't close file descriptors 0, 1,
    	or 2.
---
 sim/ppc/emul_netbsd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/sim/ppc/emul_netbsd.c b/sim/ppc/emul_netbsd.c
index 6bef370..5e39975 100644
--- a/sim/ppc/emul_netbsd.c
+++ b/sim/ppc/emul_netbsd.c
@@ -440,8 +440,13 @@ do_close(os_emul_data *emul,
 
   SYS(close);
 
-  /* Can't combine these statements, cuz close sets errno. */
-  status = close(d);
+  /* Do not close stdin, stdout, or stderr. GDB may still need access to
+     these descriptors.  */
+  if (d == 0 || d == 1 || d == 2)
+    status = 0;
+  else
+    status = close(d);
+
   emul_write_status(processor, status, errno);
 }