[PATCH] Fix target attribute handling (PR c++/81355).

[Martin Liška]

Hello.

Following patch skips empty strings in 'target' attribute.
Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.

Ready to be installed?
Martin

gcc/ChangeLog:

2017-07-13  Martin Liska  <mli...@suse.cz>

        PR c++/81355
        * attribs.c (sorted_attr_string): Skip empty strings.

gcc/testsuite/ChangeLog:

2017-07-13  Martin Liska  <mli...@suse.cz>

        PR c++/81355
        * g++.dg/other/pr81355.C: New test.
---
 gcc/attribs.c                        |  6 ++++++
 gcc/testsuite/g++.dg/other/pr81355.C | 14 ++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/other/pr81355.C



diff --git a/gcc/attribs.c b/gcc/attribs.c
index 5eb19e82795..bf8452a3cec 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -725,6 +725,9 @@ sorted_attr_string (tree arglist)
     {
       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
       size_t len = strlen (str);
+      /* Skip empty string.  */
+      if (len == 0)
+	continue;
       str_len_sum += len + 1;
       if (arg != arglist)
 	argnum++;
@@ -739,6 +742,9 @@ sorted_attr_string (tree arglist)
     {
       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
       size_t len = strlen (str);
+      /* Skip empty string.  */
+      if (len == 0)
+	continue;
       memcpy (attr_str + str_len_sum, str, len);
       attr_str[str_len_sum + len] = TREE_CHAIN (arg) ? ',' : '\0';
       str_len_sum += len + 1;
diff --git a/gcc/testsuite/g++.dg/other/pr81355.C b/gcc/testsuite/g++.dg/other/pr81355.C
new file mode 100644
index 00000000000..d52b444261c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/pr81355.C
@@ -0,0 +1,14 @@
+/* { dg-do compile { target x86_64-*-* } } */
+
+__attribute__((target("default")))
+int foo() {return 1;}
+
+__attribute__((target("arch=core2", "")))
+int foo() {return 2;}
+
+__attribute__((target("sse4.2", "", "")))
+int foo() {return 2;}
+
+int main() {
+    return foo();
+}