fortran: Ignore use statements on error [PR107426]

This fixes an access to freed memory on the testcase from the PR.
The problem comes from an invalid subroutine statement in an interface,
which is ignored and causes the following statements forming the procedure
body to be rejected.  One of them use-associates the intrinsic ISO_C_BINDING
module, which imports new symbols in a namespace that is freed at the time
the statement is rejected.  However, this creates dangling pointers as
ISO_C_BINDING is special and its import creates a reference to the imported
C_PTR symbol in the return type of the global intrinsic symbol for C_LOC
(see the function create_intrinsic_function).

This change saves and restores the list of use statements, so that rejected
use statements are removed before they have a chance to be applied to the
current namespace and create dangling pointers.

	PR fortran/107426

gcc/fortran/ChangeLog:

	* gfortran.h (gfc_save_module_list, gfc_restore_old_module_list):
	New declarations.
	* module.cc (old_module_list_tail): New global variable.
	(gfc_save_module_list, gfc_restore_old_module_list): New functions.
	(gfc_use_modules): Set module_list and old_module_list_tail.
	* parse.cc (next_statement): Save module_list before doing any work.
	(reject_statement): Restore module_list to its saved value.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pr89943_3.f90: Update error pattern.
	* gfortran.dg/pr89943_4.f90: Likewise.
	* gfortran.dg/use_31.f90: New test.

diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 26aa56b3358ac34f4ca168967b4c52c291cd123b..58505446bac5d3576b7ea6f191305fd4c9f01442 100644 (file)
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -3928,6 +3928,8 @@ void gfc_module_done_2 (void);
 void gfc_dump_module (const char *, int);
 bool gfc_check_symbol_access (gfc_symbol *);
 void gfc_free_use_stmts (gfc_use_list *);
+void gfc_save_module_list ();
+void gfc_restore_old_module_list ();
 const char *gfc_dt_lower_string (const char *);
 const char *gfc_dt_upper_string (const char *);
 

diff --git a/gcc/fortran/module.cc b/gcc/fortran/module.cc
index d1de53cbdb442744c0fc1ceffd0cf62bf0a46957..c565b84d61b7a07f1d7a4de5a7c5b0d5835db10e 100644 (file)
--- a/gcc/fortran/module.cc
+++ b/gcc/fortran/module.cc
@@ -195,7 +195,12 @@ static const char *module_name;
 /* The name of the .smod file that the submodule will write to.  */
 static const char *submodule_name;
 
+/* The list of use statements to apply to the current namespace
+   before parsing the non-use statements.  */
 static gfc_use_list *module_list;
+/* The end of the MODULE_LIST list above at the time the recognition
+   of the current statement started.  */
+static gfc_use_list **old_module_list_tail;
 
 /* If we're reading an intrinsic module, this is its ID.  */
 static intmod_id current_intmod;
@@ -7561,6 +7566,8 @@ gfc_use_modules (void)
       gfc_use_module (module_list);
       free (module_list);
     }
+  module_list = NULL;
+  old_module_list_tail = &module_list;
   gfc_rename_list = NULL;
 }
 
@@ -7584,6 +7591,30 @@ gfc_free_use_stmts (gfc_use_list *use_stmts)
 }
 
 
+/* Remember the end of the MODULE_LIST list, so that the list can be restored
+   to its previous state if the current statement is erroneous.  */
+
+void
+gfc_save_module_list ()
+{
+  gfc_use_list **tail = &module_list;
+  while (*tail != NULL)
+    tail = &(*tail)->next;
+  old_module_list_tail = tail;
+}
+
+
+/* Restore the MODULE_LIST list to its previous value and free the use
+   statements that are no longer part of the list.  */
+
+void
+gfc_restore_old_module_list ()
+{
+  gfc_free_use_stmts (*old_module_list_tail);
+  *old_module_list_tail = NULL;
+}
+
+
 void
 gfc_module_init_2 (void)
 {

diff --git a/gcc/fortran/parse.cc b/gcc/fortran/parse.cc
index a2bf328f681de2a7cc5743b2a3c6e96185f8c1c5..79c810c86ba12e6d059abfc09160b88bdb07d015 100644 (file)
--- a/gcc/fortran/parse.cc
+++ b/gcc/fortran/parse.cc
@@ -1800,6 +1800,7 @@ next_statement (void)
   locus old_locus;
 
   gfc_enforce_clean_symbol_state ();
+  gfc_save_module_list ();
 
   gfc_new_block = NULL;
 
@@ -3104,6 +3105,9 @@ reject_statement (void)
 
   gfc_reject_data (gfc_current_ns);
 
+  /* Don't queue use-association of a module if we reject the use statement.  */
+  gfc_restore_old_module_list ();
+
   gfc_new_block = NULL;
   gfc_undo_symbols ();
   gfc_clear_warning ();

diff --git a/gcc/testsuite/gfortran.dg/pr89943_3.f90 b/gcc/testsuite/gfortran.dg/pr89943_3.f90
index 38b723e24585c4947d09d95186d6db4956d238dd..84a9fb74741767812d1d0c09fe0ec5ca54690f1d 100644 (file)
--- a/gcc/testsuite/gfortran.dg/pr89943_3.f90
+++ b/gcc/testsuite/gfortran.dg/pr89943_3.f90
@@ -22,7 +22,7 @@ submodule(Foo_mod) Foo_smod
       module subroutine runFoo4C(ndim) bind(C, name="runFu")   ! { dg-error "Mismatch in BIND" }
          use, intrinsic :: iso_c_binding                 ! { dg-error "Unexpected USE statement" }
          implicit none                                   ! { dg-error "Unexpected IMPLICIT NONE statement" }
-         integer(c_int32_t) , intent(in) :: ndim         ! { dg-error "Unexpected data declaration" }
+         integer(c_int32_t) , intent(in) :: ndim         ! { dg-error "Symbol 'c_int32_t' at .1. has no IMPLICIT type" }
       end subroutine runFoo4C                            ! { dg-error " Expecting END SUBMODULE" }
 
 end submodule Foo_smod

diff --git a/gcc/testsuite/gfortran.dg/pr89943_4.f90 b/gcc/testsuite/gfortran.dg/pr89943_4.f90
index 8eba2eda17181da4d051f51abf418ab840afec7c..cb955d01c88a44e2c42f2e1d3673b7d6b5a65d40 100644 (file)
--- a/gcc/testsuite/gfortran.dg/pr89943_4.f90
+++ b/gcc/testsuite/gfortran.dg/pr89943_4.f90
@@ -23,7 +23,7 @@ submodule(Foo_mod) Foo_smod
       module function runFoo4C(ndim) bind(C, name="runFu")  ! { dg-error "Mismatch in BIND" }
          use, intrinsic :: iso_c_binding     ! { dg-error "Unexpected USE statement in" }
          implicit none                       ! { dg-error "Unexpected IMPLICIT NONE statement" }
-         integer(c_int32_t) , intent(in) :: ndim   ! { dg-error "Unexpected data declaration" }
+         integer(c_int32_t) , intent(in) :: ndim   ! { dg-error "Symbol 'c_int32_t' at .1. has no IMPLICIT type" }
       end function runFoo4C                  ! { dg-error "Expecting END SUBMODULE" }
 
 end submodule Foo_smod

diff --git a/gcc/testsuite/gfortran.dg/use_31.f90 b/gcc/testsuite/gfortran.dg/use_31.f90
new file mode 100644 (file)
index 0000000..89a9ab3
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/use_31.f90
@@ -0,0 +1,26 @@
+! { dg-do compile }
+!
+! PR fortran/107426
+! This example used to generate an ICE, caused by the use stmt from the nested
+! procedure declaration setting the result of the C_LOC global intrinsic symbol
+! to the symbol of C_PTR from ISO_C_BINDING being imported, before freeing the
+! latter symbol because of the rejection of the use statement.
+!
+! Contributed by Gerhard Steinmetz <gscfq@t-online.de>
+
+module m
+contains
+   subroutine p() bind(c)
+      use, intrinsic :: iso_c_binding
+      integer, target :: a = 1
+      type(c_ptr) :: z
+      interface
+         subroutine s(x) bind(cc)            ! { dg-error "Missing closing paren" }
+            use, intrinsic :: iso_c_binding  ! { dg-error "Unexpected USE statement in INTERFACE block" }
+            integer(c_int), value :: x       ! { dg-error "Parameter 'c_int' at .1. has not been declared" }
+         end                                 ! { dg-error "END INTERFACE statement expected" }
+      end interface
+      z = c_loc(a)
+      call s(z)
+   end
+end