RFC: C++ PATCH to adjust empty class parameter passing ABI

Message ID	570E99E6.3040603@redhat.com
State	New
Headers	show Return-Path: <gcc-patches-return-424785-incoming=patchwork.ozlabs.org@gcc.gnu.org> DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender :subject:to:references:cc:from:message-id:date:mime-version :in-reply-to:content-type; q=dns; s=default; b=tzPEa4Onf8JPkcGE5 Pjr2J8TgBnRxrmiWRW+4gU7odU5DXpVlZci7K8GrrD9276WRkZnjUNiLlYEYqmjh n4LWe0hae8hVBgocsB3A+OYVdVioU3p+HePMnYAZke2JE6eIDXritJ4gbSSdGm1g 6DBda8iM73gPQLsMfGIWbbwnKw= Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk Sender: gcc-patches-owner@gcc.gnu.org Subject: Re: RFC: C++ PATCH to adjust empty class parameter passing ABI To: Jakub Jelinek <jakub@redhat.com> References: <570D5A44.6060105@redhat.com> <20160413153217.GT19207@tucnak.redhat.com> <570E6B9B.1010200@redhat.com> Cc: gcc-patches List <gcc-patches@gcc.gnu.org>, Jonathan Wakely <jwakely@redhat.com>, "H.J. Lu" <hjl.tools@gmail.com> From: Jason Merrill <jason@redhat.com> Message-ID: <570E99E6.3040603@redhat.com> Date: Wed, 13 Apr 2016 15:11:34 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.1 MIME-Version: 1.0 In-Reply-To: <570E6B9B.1010200@redhat.com> Content-Type: multipart/mixed; boundary="------------080603020201090707010507"

commit 761983a023b5217ef831a43f423779940c788ecf Author: Jason Merrill <jason@redhat.com> Date: Tue Apr 12 13:16:50 2016 -0400 gcc/ * cfgexpand.c (pass_expand::execute): Handle attribute abi_warning. * expr.c (expand_expr_real_1): Likewise. gcc/cp/ * call.c (empty_class_msg, mark_for_abi_warning): New. (build_call_a): Use them. * decl.c (store_parm_decls): Use mark_for_abi_warning. * error.c (pp_format_to_string): New. diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c index 1341c14..4e5ccbb 100644 --- a/gcc/cfgexpand.c +++ b/gcc/cfgexpand.c @@ -73,6 +73,7 @@ along with GCC; see the file COPYING3. If not see #include "builtins.h" #include "tree-chkp.h" #include "rtl-chkp.h" +#include "langhooks.h" /* Some systems use __main in a way incompatible with its use in gcc, in these cases use the macros NAME__MAIN to give a quoted symbol and SYMBOL__MAIN to @@ -6221,6 +6222,15 @@ pass_expand::execute (function *fun) (int) PARAM_VALUE (PARAM_SSP_BUFFER_SIZE)); } + if (warn_abi) + if (tree attr = lookup_attribute ("abi_warning", + DECL_ATTRIBUTES (current_function_decl))) + warning_at (DECL_SOURCE_LOCATION (current_function_decl), + OPT_Wabi, "definition of %qs: %s", + identifier_to_locale (lang_hooks.decl_printable_name + (current_function_decl, 1)), + TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr)))); + /* Set up parameters and prepare for return, for the function. */ expand_function_start (current_function_decl); diff --git a/gcc/cp/call.c b/gcc/cp/call.c index 9cee3b7..97d790f 100644 --- a/gcc/cp/call.c +++ b/gcc/cp/call.c @@ -401,7 +401,10 @@ build_call_a (tree function, int n, tree *argarray) else if (!warned && empty_arg) { location_t loc = EXPR_LOC_OR_LOC (empty_arg, input_location); - warn_empty_class_abi (empty_arg, loc); + if (decl && !varargs_function_p (decl)) + mark_for_abi_warning (decl, empty_arg); + else + warn_empty_class_abi (empty_arg, loc); warned = true; } } @@ -7019,8 +7022,19 @@ empty_class_arg (tree val) return build2 (COMPOUND_EXPR, etype, val, empty); } -/* Warn about the change in empty class parameter passing ABI. Returns true - if we warned. */ +/* Generate a message warning about the change in empty class parameter passing ABI. */ + +static tree +empty_class_msg (tree type) +{ + if (!TYPE_P (type)) + type = TREE_TYPE (type); + + return pp_format_to_string ("empty class %qT parameter passing ABI " + "changes in -fabi-version=10 (GCC 6)", type); +} + +/* Warn immediately about the change in empty class parameter ABI. */ void warn_empty_class_abi (tree arg, location_t loc) @@ -7028,19 +7042,24 @@ warn_empty_class_abi (tree arg, location_t loc) if (!warn_abi || !abi_version_crosses (10)) return; - tree type; - if (TYPE_P (arg)) - type = arg; - else - { - if (TREE_TYPE (arg) == empty_struct_type - && TREE_CODE (arg) == COMPOUND_EXPR) - arg = TREE_OPERAND (arg, 0); - type = TREE_TYPE (arg); - } + warning_at (loc, OPT_Wabi, "%E", empty_class_msg (arg)); +} - warning_at (loc, OPT_Wabi, "empty class %qT parameter passing ABI " - "changes in -fabi-version=10 (GCC 6)", type); +/* Tack a warning about the change in empty class parameter ABI onto FN, so + that we get a warning if a definition or call is emitted. */ + +void +mark_for_abi_warning (tree fn, tree type) +{ + if (!warn_abi || !abi_version_crosses (10)) + return; + if (lookup_attribute ("abi_warning", DECL_ATTRIBUTES (fn))) + return; + + tree msg = empty_class_msg (type); + msg = build_tree_list (NULL_TREE, msg); + DECL_ATTRIBUTES (fn) = tree_cons (get_identifier ("abi_warning"), msg, + DECL_ATTRIBUTES (fn)); } /* Returns the type which will really be used for passing an argument of diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index 60abbaa..8d721c7 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -5540,6 +5540,7 @@ extern tree build_addr_func (tree, tsubst_flags_t); extern void set_flags_from_callee (tree); extern tree build_call_a (tree, int, tree*); extern tree build_call_n (tree, int, ...); +extern void mark_for_abi_warning (tree, tree); extern void warn_empty_class_abi (tree, location_t); extern bool null_ptr_cst_p (tree); extern bool null_member_pointer_value_p (tree); @@ -5895,6 +5896,7 @@ extern bool pedwarn_cxx98 (location_t, int, const char *, extern location_t location_of (tree); extern void qualified_name_lookup_error (tree, tree, tree, location_t); +extern tree pp_format_to_string (const char *, ...); /* in except.c */ extern void init_exception_processing (void); diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 0326900..7099199 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -14357,7 +14357,7 @@ store_parm_decls (tree current_function_parms) && (saw_nonempty || varargs_function_p (current_function_decl))) { - warn_empty_class_abi (parm, DECL_SOURCE_LOCATION (parm)); + mark_for_abi_warning (current_function_decl, type); warned = true; } } diff --git a/gcc/cp/error.c b/gcc/cp/error.c index aa5fd41..5aaa177 100644 --- a/gcc/cp/error.c +++ b/gcc/cp/error.c @@ -3718,3 +3718,25 @@ qualified_name_lookup_error (tree scope, tree name, suggest_alternatives_for (location, name); } } + +/* Like error et al, but return the formatted message as a STRING_CST. */ + +tree +pp_format_to_string (const char *msg, ...) +{ + pretty_printer *pp = global_dc->printer; + text_info text; + va_list ap; + + va_start (ap, msg); + text.err_no = errno; + text.args_ptr = ≈ + text.format_spec = msg; + pp_format (pp, &text); + pp_output_formatted_text (pp); + va_end (ap); + const char *fmt = pp_formatted_text (pp); + tree str = build_string (strlen (fmt) + 1, fmt); + pp_clear_output_area (pp); + return str; +} diff --git a/gcc/expr.c b/gcc/expr.c index 29d22b0..f852c51 100644 --- a/gcc/expr.c +++ b/gcc/expr.c @@ -10579,6 +10579,13 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode, 0, "%Kcall to %qs declared with attribute warning: %s", exp, identifier_to_locale (lang_hooks.decl_printable_name (fndecl, 1)), TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr)))); + if (warn_abi && fndecl + && (attr = lookup_attribute ("abi_warning", + DECL_ATTRIBUTES (fndecl))) != NULL) + warning_at (tree_nonartificial_location (exp), + OPT_Wabi, "%Kcall to %qs: %s", + exp, identifier_to_locale (lang_hooks.decl_printable_name (fndecl, 1)), + TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr)))); /* Check for a built-in function. */ if (fndecl && DECL_BUILT_IN (fndecl)) diff --git a/gcc/testsuite/g++.dg/abi/empty20.C b/gcc/testsuite/g++.dg/abi/empty20.C new file mode 100644 index 0000000..be1e826 --- /dev/null +++ b/gcc/testsuite/g++.dg/abi/empty20.C @@ -0,0 +1,25 @@ +// { dg-options "-Wabi=9 -O0" } + +struct A { }; + +void f(A, A) { } // No warning, trailing parms all empty +void f(A, A, int) { } // { dg-warning "ABI" } +__attribute__ ((always_inline)) +inline void f(A a, int i) { } // No warning, always inlined +__attribute__ ((always_inline)) +inline void f2(A a, int i) // But the call within the fn gets a warning +{ // when it's inlined into main + f(a,a,i); // { dg-warning "ABI" } +} +inline void f3(A a, int i) // This one is never called +{ + f(a,a,i); +} +int main() +{ + A a; + f(a,a); + f(a,a,42); // { dg-warning "ABI" } + f(a,42); + f2(a,42); +}

RFC: C++ PATCH to adjust empty class parameter passing ABI

Commit Message

Comments

Patch