PR10461: Probe identical functions only once

In C++ especially, a function definition in a header may be compiled
into multiple CUs, but the linker will merge those into a single output
function.  We don't want to place multiple probes on the same function.

The dupe-detection from the alias code (commit 1c6b77e5) already tracks
identical functions within a CU, so I've just lifted this to instead
track function entrypcs at the module level.

* dwflpp.cxx (dwflpp::iterate_over_functions): Remove dupe checks.
* tapsets.cxx (dwarf_query): Add alias_dupes set to the query.
  (dwarf_query::handle_query_module): Reset the dupes for each module.
  (query_dwarf_func): Check that we only probe each entrypc once.

1 files changed, 14 insertions, 0 deletions

diff --git a/tapsets.cxx b/tapsets.cxx
index 8d0e0ab2..9884860a 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -548,6 +548,9 @@ struct dwarf_query : public base_query
 		       Dwarf_Die *scope_die,
 		       Dwarf_Addr addr);
 
+  // Track addresses we've already seen in a given module
+  set<Dwarf_Addr> alias_dupes;
+
   // Extracted parameters.
   string function_val;
 
@@ -854,6 +857,9 @@ dwarf_query::handle_query_module()
   // prebuild the symbol table to resolve aliases
   dw.mod_info->get_symtab(this);
 
+  // reset the dupe-checking for each new module
+  alias_dupes.clear();
+
   if (dw.mod_info->dwarf_status == info_present)
     query_module_dwarf();
 
@@ -1272,6 +1278,14 @@ query_dwarf_func (Dwarf_Die * func, base_query * bq)
     {
       q->dw.focus_on_function (func);
 
+      // make sure that this function address hasn't
+      // already been matched under an aliased name
+      Dwarf_Addr addr;
+      if (!q->dw.func_is_inline() &&
+          dwarf_entrypc(func, &addr) == 0 &&
+          !q->alias_dupes.insert(addr).second)
+        return DWARF_CB_OK;
+
       if (q->dw.func_is_inline ()
           && (! q->has_call) && (! q->has_return)
 	  && (q->has_statement_str || q->has_function_str))