Hello,
Harald reminded me recently that there was a working patch attached to the PR.
I added a documentation comment with the hope that it may help avoid
making the same mistake in the future.
Regression tested on x86_64-pc-linux-gnu.
OK for master?
-- >8 --
Remove one reference count incrementation following the assignment of a
symbol pointer to a local variable. Most symbol pointers are "weak" pointer
and don't need any reference count update when they are assigned, and it is
especially the case of local variables.
This fixes a memory leak with the testcase from the PR (not included).
PR fortran/108957
gcc/fortran/ChangeLog:
* gfortran.h (gfc_symbol): Add comment documenting reference counting.
* parse.cc (parse_interface): Remove reference count incrementation.
---
gcc/fortran/gfortran.h | 20 ++++++++++++++++++++
gcc/fortran/parse.cc | 3 ---
2 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index f4a1c106cea..6caf7765ac6 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -1944,7 +1944,27 @@ typedef struct gfc_symbol
according to the Fortran standard. */
unsigned pass_as_value:1;
+ /* Reference counter, used for memory management.
+
+ Some symbols may be present in more than one namespace, for example
+ function and subroutine symbols are present both in the outer namespace
and
+ the procedure body namespace. Freeing symbols with the namespaces they
are
+ in would result in double free for those symbols. This field counts
+ references and is used to delay the memory release until the last
reference
+ to the symbol is removed.
+
+ Not every symbol pointer is accounted for reference counting. Fields
+ gfc_symtree::n::sym are, and gfc_finalizer::proc_sym as well. But most of
+ them (dummy arguments, generic list elements, etc) are "weak" pointers;
+ the reference count isn't updated when they are assigned, and they are
+ ignored when the surrounding structure memory is released. This is not a
+ problem because there is always a namespace as surrounding context and
+ symbols have a name they can be referred with in that context, so the
+ namespace keeps the symbol from being freed, keeping the pointer valid.
+ When the namespace ceases to exist, and the symbols with it, the other
+ structures referencing symbols cease to exist as well. */
int refs;
+
struct gfc_namespace *ns; /* namespace containing this symbol */
tree backend_decl;
diff --git a/gcc/fortran/parse.cc b/gcc/fortran/parse.cc
index 8f09ddf753c..58386805ffe 100644
--- a/gcc/fortran/parse.cc
+++ b/gcc/fortran/parse.cc
@@ -4064,9 +4064,6 @@ loop:
accept_statement (st);
prog_unit = gfc_new_block;
prog_unit->formal_ns = gfc_current_ns;
- if (prog_unit == prog_unit->formal_ns->proc_name
- && prog_unit->ns != prog_unit->formal_ns)
- prog_unit->refs++;
decl:
/* Read data declaration statements. */
--
2.40.1
