* mpicoder.c (do_get_buffer): Avoid zero length allocation.

Checked that all callers behave properly when NBYTES returns 0 as
the length of the allocated buffer.

2 files changed, 12 insertions, 3 deletions

diff --git a/mpi/ChangeLog b/mpi/ChangeLog
index 238f69f31..0a2d05b64 100644
--- a/mpi/ChangeLog
+++ b/mpi/ChangeLog
@@ -1,3 +1,9 @@
+2002-09-20  Werner Koch  <[email protected]>
+
+	* mpicoder.c (do_get_buffer): Avoid zero length allocation.
+	Checked that all callers behave properly when NBYTES returns 0 as
+	the length of the allocated buffer.
+
 2002-09-10  Werner Koch  <[email protected]>
 
 	* mpi-bit.c (mpi_normalize): Replaced the check for protected by
diff --git a/mpi/mpicoder.c b/mpi/mpicoder.c
index f796888c8..8cb1538c0 100644
--- a/mpi/mpicoder.c
+++ b/mpi/mpicoder.c
@@ -332,12 +332,15 @@ do_get_buffer( MPI a, unsigned *nbytes, int *sign, int force_secure )
     byte *p, *buffer;
     mpi_limb_t alimb;
     int i;
+    unsigned int n;
 
     if( sign )
 	*sign = a->sign;
-    *nbytes = a->nlimbs * BYTES_PER_MPI_LIMB;
-    p = buffer = force_secure || mpi_is_secure(a) ? m_alloc_secure( *nbytes)
-						  : m_alloc( *nbytes );
+    *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
+    if (!n)
+      n++; /* avoid zero length allocation */
+    p = buffer = force_secure || mpi_is_secure(a) ? m_alloc_secure(n)
+						  : m_alloc(n);
 
     for(i=a->nlimbs-1; i >= 0; i-- ) {
 	alimb = a->d[i];