Hi!
25.02.2020 13:36, Roman Zhuykov wrote:
> So, IMHO the best next step is to improve the behavior rather then docs :)
I want to add one more point into this discussion. I have recently
decided to test some stuff on old branches, e.q gcc-4.9, 5 and 6.
On modern systems there are some issues with building old branches, at
least I met "struct ucontext -> ucontext_t",
"sys/ustat.h - no such file" and few others. But in this particular
experiment, I was using pretty old Ubuntu 16.04,
and there were no issues with building unpatched frozen branches.
But, since the stuff was really experimental, at some moment I've
decided to apply the following to enable more checking:
diff --git a/gcc/DEV-PHASE b/gcc/DEV-PHASE
--- a/gcc/DEV-PHASE
+++ b/gcc/DEV-PHASE
@@ -0,0 +1 @@
+experimental
diff --git a/gcc/configure b/gcc/configure
--- a/gcc/configure
+++ b/gcc/configure
@@ -6727,7 +6727,7 @@ do
# these set all the flags to specific states
yes) ac_assert_checking=1 ; ac_checking=1 ; ac_df_checking= ;
ac_fold_checking= ; ac_gc_checking=1 ;
- ac_gc_always_collect= ; ac_gimple_checking=1 ;
ac_rtl_checking= ;
+ ac_gc_always_collect= ; ac_gimple_checking=1 ;
ac_rtl_checking=1 ;
ac_rtlflag_checking=1 ; ac_runtime_checking=1 ;
ac_tree_checking=1 ; ac_valgrind_checking= ;
ac_types_checking=1 ;;
diff --git a/gcc/configure.ac b/gcc/configure.ac
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -427,7 +427,7 @@ do
# these set all the flags to specific states
yes) ac_assert_checking=1 ; ac_checking=1 ; ac_df_checking= ;
ac_fold_checking= ; ac_gc_checking=1 ;
- ac_gc_always_collect= ; ac_gimple_checking=1 ;
ac_rtl_checking= ;
+ ac_gc_always_collect= ; ac_gimple_checking=1 ;
ac_rtl_checking=1 ;
ac_rtlflag_checking=1 ; ac_runtime_checking=1 ;
ac_tree_checking=1 ; ac_valgrind_checking= ;
ac_types_checking=1 ;;
And that gives broken basic x86_64 bootstrap on gcc-5 and gcc-6 branches!
First, about gcc-4.9 branch, it works fine. There was another story
that it failed with rtl checks on ppc64. Alex told me there was some
moment when all folks forgot to test that. So, everything went fine
after backporting r243144 (r5-10072) and r212829 (r5-1977).
But the gcc-5 branch case was much more tricky. The following 3 hunks
are needed to fix x86_64 bootstrap.
And that one with UNKNOWN_LOCATION is really a null pointer dereference
we put into a released compiler!
diff --git a/gcc/fortran/frontend-passes.c b/gcc/fortran/frontend-passes.c
--- a/gcc/fortran/frontend-passes.c
+++ b/gcc/fortran/frontend-passes.c
@@ -138,7 +138,7 @@ gfc_run_passes (gfc_namespace *ns)
*/
static int
-realloc_string_callback (gfc_code **c, int *walk_subtrees,
+realloc_string_callback (gfc_code **c, int *walk_subtrees ATTRIBUTE_UNUSED,
void *data ATTRIBUTE_UNUSED)
{
gfc_expr *expr1, *expr2;
diff --git a/gcc/fortran/trans-openmp.c b/gcc/fortran/trans-openmp.c
--- a/gcc/fortran/trans-openmp.c
+++ b/gcc/fortran/trans-openmp.c
@@ -38,7 +38,6 @@ along with GCC; see the file COPYING3. If not see
#include "gimplify.h" /* For create_tmp_var_raw. */
#include "stringpool.h"
#include "gfortran.h"
-#include "diagnostic-core.h" /* For internal_error. */
#include "trans.h"
#include "trans-stmt.h"
#include "trans-types.h"
diff --git a/gcc/toplev.c b/gcc/toplev.c
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1386,8 +1386,7 @@ process_options (void)
if (flag_sanitize & SANITIZE_THREAD)
{
- error (UNKNOWN_LOCATION,
- "%<-fcheck-pointer-bounds%> is not supported with "
+ error ("%<-fcheck-pointer-bounds%> is not supported with "
"Thread Sanitizer");
flag_check_pointer_bounds = 0;
In gcc-6 branch the solution was simple - I have to revert r262046
(r6-10168), haven't investigate that deeply.
Overall, IMHO this is one more point to review current
branching/checking approach.
So, I understand that main purpose of empty DEV-PHASE is to test "almost
released" compiler in the same way it will be compiled from release
archives.
But those issues show it's also necessary to run checking-bootstrap when
backporting any patch.
PS. Everything seems fine in gcc-7 branch.
Roman
