dom0-build: fix build with clang5

With non-empty CONFIG_DOM0_MEM clang5 produces

dom0_build.c:344:24: error: use of logical '&&' with constant operand [-Werror,-Wconstant-logical-operand]
    if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
                       ^  ~~~~~~~~~~~~~~~~~~
dom0_build.c:344:24: note: use '&' for a bitwise operation
    if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
                       ^~
                       &
dom0_build.c:344:24: note: remove constant to silence this warning
    if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
                      ~^~~~~~~~~~~~~~~~~~~~~
1 error generated.

Obviously neither of the two suggestions are an option here. Oddly
enough swapping the operands of the && helps, while e.g. casting or
parenthesizing doesn't. Another workable variant looks to be the use of
!! on the constant.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <julien@xen.org>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index d2d11eda2682e8a406774cb077000abd0fdf15b3..4307087536423abe389530463155fcc4b5126e02 100644 (file)
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2514,7 +2514,8 @@ int __init construct_dom0(struct domain *d)
 
     printk("*** LOADING DOMAIN 0 ***\n");
 
-    if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
+    /* The ordering of operands is to work around a clang5 issue. */
+    if ( CONFIG_DOM0_MEM[0] && !dom0_mem_set )
         parse_dom0_mem(CONFIG_DOM0_MEM);
 
     if ( dom0_mem <= 0 )

diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
index 6bf53655820208b50a4f8fe72a03039e856192b4..0ce29e91a317761802fef01aa79c47b3eabd2e09 100644 (file)
--- a/xen/arch/x86/dom0_build.c
+++ b/xen/arch/x86/dom0_build.c
@@ -318,7 +318,8 @@ unsigned long __init dom0_compute_nr_pages(
     unsigned long avail = 0, nr_pages, min_pages, max_pages;
     bool need_paging;
 
-    if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] )
+    /* The ordering of operands is to work around a clang5 issue. */
+    if ( CONFIG_DOM0_MEM[0] && !dom0_mem_set )
         parse_dom0_mem(CONFIG_DOM0_MEM);
 
     for_each_node_mask ( node, dom0_nodes )