PR11004: try / catch error-handling script syntax

* parse.h (try_block): New class.  Update basic visitors.
* staptree.cxx: Implement basic visitors.
* parse.cxx (expect_kw): Fix to actually look for keywords.
  (parse_try_block): New function.
  (lexer ctor): Designate 'try' and 'catch' as keywords.
* elaborate.cxx (dead_assignment_remover, dead_statmtexpr_remover): Optimize.
  (other visitors): Implement.
* translate.cxx (c_unparser): Implement via super-handy __local__ labels.
  (emit_probe, emit_function): Make outer out: label also __local__.
* testsuite/buildok/fortyone.stp, semko/fortynine.stp,
  systemtap.base/trycatch.exp: Test it.
* NEWS, doc/langref.txt, stap.1.in: Document it.

1 files changed, 54 insertions, 0 deletions

diff --git a/elaborate.cxx b/elaborate.cxx
index a2ab8522..72f12baf 100644
--- a/elaborate.cxx
+++ b/elaborate.cxx
@@ -2206,6 +2206,7 @@ struct dead_assignment_remover: public update_visitor
     session(s), relaxed_p(r), vut(v) {}
 
   void visit_assignment (assignment* e);
+  void visit_try_block (try_block *s);
 };
 
 
@@ -2262,6 +2263,27 @@ dead_assignment_remover::visit_assignment (assignment* e)
   provide (e);
 }
 
+
+void
+dead_assignment_remover::visit_try_block (try_block *s)
+{
+  replace (s->try_block);
+  if (s->catch_error_var)
+    {
+      vardecl* errvar = s->catch_error_var->referent;
+      if (vut.read.find(errvar) == vut.read.end()) // never read?
+        {
+          if (session.verbose>2)
+            clog << "Eliding unused error string catcher " << errvar->name
+                 << " at " << *s->tok << endl;
+          s->catch_error_var = 0;
+        }
+    }
+  replace (s->catch_block);
+  provide (s);
+}
+
+
 // Let's remove assignments to variables that are never read.  We
 // rewrite "(foo = expr)" as "(expr)".  This makes foo a candidate to
 // be optimized away as an unused variable, and expr a candidate to be
@@ -2301,6 +2323,7 @@ struct dead_stmtexpr_remover: public update_visitor
     session(s), relaxed_p(r) {}
 
   void visit_block (block *s);
+  void visit_try_block (try_block *s);
   void visit_null_statement (null_statement *s);
   void visit_if_statement (if_statement* s);
   void visit_foreach_loop (foreach_loop *s);
@@ -2363,6 +2386,22 @@ dead_stmtexpr_remover::visit_block (block *s)
   provide (s);
 }
 
+
+void
+dead_stmtexpr_remover::visit_try_block (try_block *s)
+{
+  replace (s->try_block, true);
+  replace (s->catch_block, true); // null catch{} is ok and useful
+  if (s->try_block == 0)
+    {
+      if (session.verbose>2)
+        clog << "Eliding empty try {} block " << *s->tok << endl;
+      s = 0;
+    }
+  provide (s);
+}
+
+
 void
 dead_stmtexpr_remover::visit_if_statement (if_statement *s)
 {
@@ -4262,6 +4301,21 @@ typeresolution_info::visit_block (block* e)
 
 
 void
+typeresolution_info::visit_try_block (try_block* e)
+{
+  if (e->try_block)
+    e->try_block->visit (this);
+  if (e->catch_error_var)
+    {
+      t = pe_string;
+      e->catch_error_var->visit (this);
+    }
+  if (e->catch_block)
+    e->catch_block->visit (this);
+}
+
+
+void
 typeresolution_info::visit_embeddedcode (embeddedcode*)
 {
 }