This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH][RFC] Instrument function exit with __builtin_unreachable in C++.
On 10/18/2017 02:52 PM, Marek Polacek wrote:
> On Wed, Oct 18, 2017 at 02:46:23PM +0200, Martin Liška wrote:
>> On 10/12/2017 10:48 AM, Jakub Jelinek wrote:
>>> On Thu, Oct 12, 2017 at 10:40:42AM +0200, Martin Liška wrote:
>>>> --- a/gcc/cp/constexpr.c
>>>> +++ b/gcc/cp/constexpr.c
>>>> @@ -1175,7 +1175,12 @@ cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun,
>>>> {
>>>> new_call = build_call_array_loc (EXPR_LOCATION (t), TREE_TYPE (t),
>>>> CALL_EXPR_FN (t), nargs, args);
>>>> - error ("%q+E is not a constant expression", new_call);
>>>> +
>>>> + /* Do not allow__builtin_unreachable in constexpr function. */
>>>> + if (DECL_FUNCTION_CODE (fun) == BUILT_IN_UNREACHABLE)
>>>
>>> As I said earlier, I think it would be better to differentiate between
>>> explicit __builtin_unreachable and the implicitly added one from the patch.
>>> So this could be done as
>>> if (DECL_FUNCTION_CODE (fun) == BUILT_IN_UNREACHABLE
>>> && EXPR_LOCATION (t) == BUILTINS_LOCATION)
>>>
>>>> + location_t loc = DECL_SOURCE_LOCATION (fndecl);
>>>> + if (sanitize_flags_p (SANITIZE_RETURN, fndecl))
>>>> + t = ubsan_instrument_return (loc);
>>>> + else
>>>> + t = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_UNREACHABLE),
>>>
>>> and here use BUILTINS_LOCATION instead of loc.
>>> The code might be more readable by doing:
>>> {
>>> tree fndecl = builtin_decl_explicit (BUILT_IN_UNREACHABLE);
>>> t = build_call_expr_loc (BUILTINS_LOCATION, fndecl, 0);
>>> }
>>>
>>>> + 0);
>>>> +
>>>
>>> Jakub
>>>
>>
>> Hi.
>>
>> I'm sending updated version of the patch that should address it.
>>
>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>>
>> Ready to be installed?
>> Martin
>
>> From 36f3f45d9fa42344261faf60bb3cfbe22ed262ac Mon Sep 17 00:00:00 2001
>> From: marxin <mliska@suse.cz>
>> Date: Thu, 12 Oct 2017 10:14:59 +0200
>> Subject: [PATCH 1/3] Instrument function exit with __builtin_unreachable in
>> C++
>>
>> gcc/c-family/ChangeLog:
>>
>> 2017-10-12 Martin Liska <mliska@suse.cz>
>>
>> PR middle-end/82404
>> * c-opts.c (c_common_post_options): Set -Wreturn-type for C++
>> FE.
>> * c.opt: Set default value of warn_return_type.
>>
>> gcc/cp/ChangeLog:
>>
>> 2017-10-12 Martin Liska <mliska@suse.cz>
>>
>> PR middle-end/82404
>> * constexpr.c (cxx_eval_builtin_function_call): Handle
>> __builtin_unreachable call.
>> * cp-gimplify.c (cp_ubsan_maybe_instrument_return): Rename to
>> ...
>> (cp_maybe_instrument_return): ... this.
>> (cp_genericize): Call the function unconditionally.
>>
>> gcc/fortran/ChangeLog:
>>
>> 2017-10-12 Martin Liska <mliska@suse.cz>
>>
>> PR middle-end/82404
>> * options.c (gfc_post_options): Set default value of
>> -Wreturn-type to false.
>> ---
>> gcc/c-family/c-opts.c | 3 +++
>> gcc/c-family/c.opt | 2 +-
>> gcc/cp/constexpr.c | 8 +++++++-
>> gcc/cp/cp-gimplify.c | 20 ++++++++++++++------
>> gcc/fortran/options.c | 3 +++
>> 5 files changed, 28 insertions(+), 8 deletions(-)
>>
>> diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
>> index 6bd535532d3..682d7a83ec5 100644
>> --- a/gcc/c-family/c-opts.c
>> +++ b/gcc/c-family/c-opts.c
>> @@ -978,6 +978,9 @@ c_common_post_options (const char **pfilename)
>> flag_extern_tls_init = 1;
>> }
>>
>> + if (warn_return_type == -1)
>> + warn_return_type = c_dialect_cxx () ? 1 : 0;
>
> Here you can simply
>
> warn_return_type = c_dialect_cxx ();
>
> no?
>
> Marek
>
Yes, thanks for the nit.
Martin
>From 8bbb75392d13430ce43cc1c0572ec5506d8a4353 Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Thu, 12 Oct 2017 10:14:59 +0200
Subject: [PATCH 1/3] Instrument function exit with __builtin_unreachable in
C++
gcc/c-family/ChangeLog:
2017-10-12 Martin Liska <mliska@suse.cz>
PR middle-end/82404
* c-opts.c (c_common_post_options): Set -Wreturn-type for C++
FE.
* c.opt: Set default value of warn_return_type.
gcc/cp/ChangeLog:
2017-10-12 Martin Liska <mliska@suse.cz>
PR middle-end/82404
* constexpr.c (cxx_eval_builtin_function_call): Handle
__builtin_unreachable call.
* cp-gimplify.c (cp_ubsan_maybe_instrument_return): Rename to
...
(cp_maybe_instrument_return): ... this.
(cp_genericize): Call the function unconditionally.
gcc/fortran/ChangeLog:
2017-10-12 Martin Liska <mliska@suse.cz>
PR middle-end/82404
* options.c (gfc_post_options): Set default value of
-Wreturn-type to false.
---
gcc/c-family/c-opts.c | 3 +++
gcc/c-family/c.opt | 2 +-
gcc/cp/constexpr.c | 8 +++++++-
gcc/cp/cp-gimplify.c | 20 ++++++++++++++------
gcc/fortran/options.c | 3 +++
5 files changed, 28 insertions(+), 8 deletions(-)
diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index 6bd535532d3..2b94128e941 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -978,6 +978,9 @@ c_common_post_options (const char **pfilename)
flag_extern_tls_init = 1;
}
+ if (warn_return_type == -1)
+ warn_return_type = c_dialect_cxx ();
+
if (num_in_fnames > 1)
error ("too many filenames given. Type %s --help for usage",
progname);
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 13d2a59b8a5..e26fba734c0 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -960,7 +960,7 @@ C++ ObjC++ Var(warn_reorder) Warning LangEnabledBy(C++ ObjC++,Wall)
Warn when the compiler reorders code.
Wreturn-type
-C ObjC C++ ObjC++ Var(warn_return_type) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
+C ObjC C++ ObjC++ Var(warn_return_type) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall) Init(-1)
Warn whenever a function's return type defaults to \"int\" (C), or about inconsistent return types (C++).
Wscalar-storage-order
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 59192829d71..15253ffad9d 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1182,7 +1182,13 @@ cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun,
{
new_call = build_call_array_loc (EXPR_LOCATION (t), TREE_TYPE (t),
CALL_EXPR_FN (t), nargs, args);
- error ("%q+E is not a constant expression", new_call);
+
+ /* Do not allow__builtin_unreachable in constexpr function. */
+ if (DECL_FUNCTION_CODE (fun) == BUILT_IN_UNREACHABLE
+ && EXPR_LOCATION (t) == BUILTINS_LOCATION)
+ error ("constexpr call flows off the end of the function");
+ else
+ error ("%q+E is not a constant expression", new_call);
}
*non_constant_p = true;
return t;
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index 262485a5c1f..014c1ee7231 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -1556,10 +1556,11 @@ cp_genericize_tree (tree* t_p, bool handle_invisiref_parm_p)
/* If a function that should end with a return in non-void
function doesn't obviously end with return, add ubsan
- instrumentation code to verify it at runtime. */
+ instrumentation code to verify it at runtime. If -fsanitize=return
+ is not enabled, instrument __builtin_unreachable. */
static void
-cp_ubsan_maybe_instrument_return (tree fndecl)
+cp_maybe_instrument_return (tree fndecl)
{
if (VOID_TYPE_P (TREE_TYPE (TREE_TYPE (fndecl)))
|| DECL_CONSTRUCTOR_P (fndecl)
@@ -1600,7 +1601,16 @@ cp_ubsan_maybe_instrument_return (tree fndecl)
tree *p = &DECL_SAVED_TREE (fndecl);
if (TREE_CODE (*p) == BIND_EXPR)
p = &BIND_EXPR_BODY (*p);
- t = ubsan_instrument_return (DECL_SOURCE_LOCATION (fndecl));
+
+ location_t loc = DECL_SOURCE_LOCATION (fndecl);
+ if (sanitize_flags_p (SANITIZE_RETURN, fndecl))
+ t = ubsan_instrument_return (loc);
+ else
+ {
+ tree fndecl = builtin_decl_explicit (BUILT_IN_UNREACHABLE);
+ t = build_call_expr_loc (BUILTINS_LOCATION, fndecl, 0);
+ }
+
append_to_statement_list (t, p);
}
@@ -1674,9 +1684,7 @@ cp_genericize (tree fndecl)
walk_tree's hash functionality. */
cp_genericize_tree (&DECL_SAVED_TREE (fndecl), true);
- if (sanitize_flags_p (SANITIZE_RETURN)
- && current_function_decl != NULL_TREE)
- cp_ubsan_maybe_instrument_return (fndecl);
+ cp_maybe_instrument_return (fndecl);
/* Do everything else. */
c_genericize (fndecl);
diff --git a/gcc/fortran/options.c b/gcc/fortran/options.c
index f7bbd7f2cde..59e7f028b09 100644
--- a/gcc/fortran/options.c
+++ b/gcc/fortran/options.c
@@ -430,6 +430,9 @@ gfc_post_options (const char **pfilename)
gfc_fatal_error ("Maximum subrecord length cannot exceed %d",
MAX_SUBRECORD_LENGTH);
+ if (warn_return_type == -1)
+ warn_return_type = 0;
+
gfc_cpp_post_options ();
if (gfc_option.allow_std & GFC_STD_F2008)
--
2.14.2