[PATCH][gensupport]: Don't segfault on empty attrs list

[Tamar Christina via Gcc-patches]

Hi All,

Currently we segfault when len == 0 for an attribute list.

essentially [cons: =0, 1, 2, 3; attrs: ] segfaults but should be equivalent to
[cons: =0, 1, 2, 3] and [cons: =0, 1, 2, 3; attrs:].  This fixes it by just
returning early and leaving it to the validators whether this should error out
or not.

Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Ok for master?

Thanks,
Tamar

gcc/ChangeLog:

        * gensupport.cc (conlist): Support length 0 attribute.

--- inline copy of patch -- 
diff --git a/gcc/gensupport.cc b/gcc/gensupport.cc
index 
959d1d9c83cf397fcb344e8d3db0f339a967587f..5c5f1cf4781551d3db95103c19cd1b70d98f4f73
 100644
--- a/gcc/gensupport.cc
+++ b/gcc/gensupport.cc
@@ -619,6 +619,9 @@ public:
      [ns..ns + len) should equal XSTR (rtx, 0).  */
   conlist (const char *ns, unsigned int len, bool numeric)
   {
+    if (len == 0)
+      return;
+
     /* Trim leading whitespaces.  */
     while (ISBLANK (*ns))
       {




-- 

diff --git a/gcc/gensupport.cc b/gcc/gensupport.cc
index 
959d1d9c83cf397fcb344e8d3db0f339a967587f..5c5f1cf4781551d3db95103c19cd1b70d98f4f73
 100644
--- a/gcc/gensupport.cc
+++ b/gcc/gensupport.cc
@@ -619,6 +619,9 @@ public:
      [ns..ns + len) should equal XSTR (rtx, 0).  */
   conlist (const char *ns, unsigned int len, bool numeric)
   {
+    if (len == 0)
+      return;
+
     /* Trim leading whitespaces.  */
     while (ISBLANK (*ns))
       {