From 1ece76f5289a5dbb2bc4f221b0ba9784eff62a78 Mon Sep 17 00:00:00 2001
From: Nick Dingle <nick.dingle@arm.com>
Date: Wed, 8 Apr 2026 14:48:29 +0100
Subject: [PATCH] Calculate CUNMLQ LWORK consistently when K=0

CUNMLQ's documentation says LWORK must be:

          If SIDE = 'L', LWORK >= max(1,N);
          if SIDE = 'R', LWORK >= max(1,M).

In the current implementation, however, when K=0 a workspace query
will return LWORK=1 in WORK(1). This means a subsequent call to CUNMLQ
with a workspace of that size will fail with INFO = -12.

The other ???MLQ routines return consistent values of LWORK when K=0
(that is, equal to or greater than NW) so this patch makes CUNMLQ's
behaviour match theirs.
---
 SRC/cunmlq.f | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/SRC/cunmlq.f b/SRC/cunmlq.f
index 9b41794fc..d80e31758 100644
--- a/SRC/cunmlq.f
+++ b/SRC/cunmlq.f
@@ -243,14 +243,10 @@ SUBROUTINE CUNMLQ( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
 *
 *        Compute the workspace requirements
 *
-         IF( M.EQ.0 .OR. N.EQ.0 .OR. K.EQ.0 ) THEN
-            LWKOPT = 1
-         ELSE
-            NB = MIN( NBMAX, ILAENV( 1, 'CUNMLQ', SIDE // TRANS, M,
-     $                N,
-     $                               K, -1 ) )
-            LWKOPT = NW*NB + TSIZE
-         END IF
+        NB = MIN( NBMAX, ILAENV( 1, 'CUNMLQ', SIDE // TRANS, M, N,
+     $             K,
+     $        -1 ) )
+         LWKOPT = NW*NB + TSIZE
          WORK( 1 ) = SROUNDUP_LWORK(LWKOPT)
       END IF
 *
@@ -264,6 +260,7 @@ SUBROUTINE CUNMLQ( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
 *     Quick return if possible
 *
       IF( M.EQ.0 .OR. N.EQ.0 .OR. K.EQ.0 ) THEN
+         WORK( 1 ) = 1
          RETURN
       END IF
 *