Allow CONFIG_foo COMPARISON-OP CONFIG_bar in preprocessor conditionals.

* parse.cxx (eval_pp_conditional): If rhs and lhs are both CONFIG_...
  identifiers try to convert them both to numbers or otherwise threat
  them both as strings for eval_comparison.
* testsuite/semok/config_config.stp: New test.

2 files changed, 43 insertions, 2 deletions

diff --git a/parse.cxx b/parse.cxx
index a7b3ebd7..ad4f93f0 100644
--- a/parse.cxx
+++ b/parse.cxx
@@ -185,6 +185,7 @@ bool eval_comparison (const OPERAND& lhs, const token* op, const OPERAND& rhs)
 //                 or: arch COMPARISON-OP "arch-string"
 //                 or: CONFIG_foo COMPARISON-OP "config-string"
 //                 or: CONFIG_foo COMPARISON-OP number
+//                 or: CONFIG_foo COMPARISON-OP CONFIG_bar
 //                 or: "string1" COMPARISON-OP "string2"
 //                 or: number1 COMPARISON-OP number2
 // The %: ELSE-TOKENS part is optional.
@@ -304,9 +305,32 @@ bool eval_pp_conditional (systemtap_session& s,
 	  int64_t rhs = lex_cast<int64_t>(r->content);
 	  return eval_comparison (lhs, op, rhs);
 	}
+      else if (r->type == tok_identifier
+	       && r->content.substr(0,7) == "CONFIG_")
+	{
+	  // First try to convert both to numbers,
+	  // otherwise threat both as strings.
+          const char* startp = s.kernel_config[l->content].c_str ();
+          char* endp = (char*) startp;
+          errno = 0;
+          int64_t val = (int64_t) strtoll (startp, & endp, 0);
+          if (errno != ERANGE && errno != EINVAL && *endp == '\0')
+	    {
+	      int64_t lhs = val;
+	      startp = s.kernel_config[r->content].c_str ();
+	      endp = (char*) startp;
+	      errno = 0;
+	      int64_t rhs = (int64_t) strtoll (startp, & endp, 0);
+	      if (errno != ERANGE && errno != EINVAL && *endp == '\0')
+		return eval_comparison (lhs, op, rhs);
+	    }
+
+	  string lhs = s.kernel_config[l->content];
+	  string rhs = s.kernel_config[r->content];
+	  return eval_comparison (lhs, op, rhs);
+	}
       else
-	throw parse_error ("expected string or number literal as right value",
-			   r);
+	throw parse_error ("expected string, number literal or other CONFIG_... as right value", r);
     }
   else if (l->type == tok_string && r->type == tok_string)
     {
diff --git a/testsuite/semok/config_config.stp b/testsuite/semok/config_config.stp
new file mode 100755
index 00000000..287931e2
--- /dev/null
+++ b/testsuite/semok/config_config.stp
@@ -0,0 +1,17 @@
+#! stap -p2
+
+# check that CONFIGs can match other CONFIGS.
+probe
+  %( CONFIG_HZ == CONFIG_NR_CPUS
+     || CONFIG_NR_CPUS > CONFIG_HZ
+     || CONFIG_NR_CPUS < CONFIG_HZ %?
+    %( CONFIG_NFSD == CONFIG_NFS_COMMON
+       || CONFIG_NFS_COMMON != CONFIG_NFSD
+    %? begin
+    %: noprobe
+    %)
+  %: nonoprobe
+  %)
+{
+  exit()
+}