Fix crash accessing builtins in sanitizer.def and after (PR jit/82174)

Calls to gcc_jit_context_get_builtin_function that accessed builtins
in sanitizer.def and after (or failed to match any builtin) led to
a crash accessing a NULL builtin name.

The entries with the NULL name came from these lines in sanitizer.def:

  /* This has to come before all the sanitizer builtins.  */
  DEF_BUILTIN_STUB(BEGIN_SANITIZER_BUILTINS, (const char *)0)

  [...snip...]

  /* This has to come after all the sanitizer builtins.  */
  DEF_BUILTIN_STUB(END_SANITIZER_BUILTINS, (const char *)0)

This patch updates jit-builtins.c to cope with such entries, fixing the
crash.

gcc/jit/ChangeLog:
	PR jit/82174
	* jit-builtins.c (matches_builtin): Ignore entries with a NULL
	name.

gcc/testsuite/ChangeLog:
	PR jit/82174
	* jit.dg/test-error-gcc_jit_context_get_builtin_function-unknown-builtin.c:
	New test case.

From-SVN: r252769

gcc/jit/ChangeLog

+2017-09-14  David Malcolm  <dmalcolm@redhat.com>
+
+	PR jit/82174
+	* jit-builtins.c (matches_builtin): Ignore entries with a NULL
+	name.
+
 2017-08-18  David Malcolm  <dmalcolm@redhat.com>
 
 	PR tree-optimization/46805

gcc/jit/jit-builtins.c

@@ -68,7 +68,10 @@ matches_builtin (const char *in_name,
 		 const struct builtin_data& bd)
 {
   const bool debug = 0;
-  gcc_assert (bd.name);
+
+  /* Ignore entries with a NULL name.  */
+  if (!bd.name)
+    return false;
 
   if (debug)
     fprintf (stderr, "seen builtin: %s\n", bd.name);

gcc/testsuite/ChangeLog

+2017-09-14  David Malcolm  <dmalcolm@redhat.com>
+
+	PR jit/82174
+	* jit.dg/test-error-gcc_jit_context_get_builtin_function-unknown-builtin.c:
+	New test case.
+
 2017-09-14  Pat Haugen  <pthaugen@us.ibm.com>
 
 	* gcc.target/powerpc/r2_shrink-wrap.c: New.

gcc/testsuite/jit.dg/test-error-gcc_jit_context_get_builtin_function-unknown-builtin.c

+#include <stdlib.h>
+#include <stdio.h>
+
+#include "libgccjit.h"
+
+#include "harness.h"
+
+void
+create_code (gcc_jit_context *ctxt, void *user_data)
+{
+  gcc_jit_context_get_builtin_function (ctxt,
+					"this_is_not_a_builtin");
+}
+
+void
+verify_code (gcc_jit_context *ctxt, gcc_jit_result *result)
+{
+  CHECK_VALUE (result, NULL);
+
+  CHECK_STRING_VALUE (gcc_jit_context_get_first_error (ctxt),
+		      "builtin \"this_is_not_a_builtin\" not found");
+}