Internal error in find_local_static_variable_init in strict C++03 mode

[thinkoid]

Issue Summary

cpfe fails an assertion on a small, valid C++03 program under -A. g++ and clang++ accept it with -std=c++98 -pedantic.

Reproducing Source Code

struct D { ~D (); };
static int f (int m) {
  static const int a[] = { 1 };
  if (m) return a[0];
  D d;
  return 0;
}
int g () { return f (1); }

Command-line Options

cpfe -A t.cpp

Type of Issue

[Front End] This code SHOULD compile with these options.

Additional Details

"t.cpp", line 4 (col. 10): internal error: assertion failed:
          find_local_static_variable_init: none found for specified variable
          and scope (il.c, line 17273 in find_local_static_variable_init)

It also crashes under -a. It compiles with -A --no_export, --export, no options, and --c++11 -A. linux-gcc-debug does not reproduce it. Seen at e24bb9a.

Probable cause: with export enabled, lowering of f waits for a module id (must_wait_for_module_id), so set_block_scope_parents runs before lowering. Lowering then adds a block scope for the return-value temporary (add_temporary_to_scope, lower_il.c:1651) and never sets its parent. The C back end looks up a's initializer from that block and cannot reach f's scope. Debug builds add checking pragmas to function scopes, so add_temporary_to_scope adds no block there.

Testing of the patch below: the six option sets on the linux-gcc-release, linux-gcc-debuggable-release and linux-gcc-debug presets; 15 variants of the reproducer and the original 19,000-line source; a run-time variant whose output matches g++; edgy --no-flakey-tests all at f0e30b6 (same lower_il.c), with logs identical to an unpatched run.

--- a/src/lower_il.c
+++ b/src/lower_il.c
@@ -1654,6 +1654,10 @@ in the user's program.
           block->assoc_scope = scope;
           scope->assoc_block = stmt;
           parent_scope->scopes = scope;
+          /* Set the parent here: when lowering is delayed (e.g., waiting for
+             a module id), set_block_scope_parents has already run for this
+             function and will not run again. */
+          scope->parent = parent_scope;
         }  /* if */
       }  /* if */
     }  /* if */

Reproducing (Standard) Configuration(s)

linux-gcc-release, linux-gcc-debuggable-release

Reproducing (Non-standard) Configuration

No response

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