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PR c++/67445 - returning temporary initializer_list.

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PR c++/67711 - assigning from temporary initializer_list.
	PR c++/48562 - new initializer_list.
	* typeck.c (maybe_warn_about_returning_address_of_local): Also warn
	about returning local initializer_list.
	* cp-tree.h (AUTO_TEMP_NAME, TEMP_NAME_P): Remove.
	* call.c (build_over_call): Warn about assignment from temporary
	init_list.
	* init.c (build_new_1): Warn about 'new std::initializer_list'.
	(find_list_begin, maybe_warn_list_ctor): New.
	(perform_member_init): Use maybe_warn_list_ctor.

From-SVN: r260905
This commit is contained in:
Jason Merrill 2018-05-29 16:04:52 -04:00 committed by Jason Merrill
parent 5d2e68ea0a
commit 04eb9c5574
18 changed files with 292 additions and 57 deletions
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4
gcc/c-family/ChangeLog
View File

@ -1,3 +1,7 @@
2018-05-29 Jason Merrill <jason@redhat.com>
* c.opt (Winit-list-lifetime): New flag.
2018-05-28 Bernd Edlinger <bernd.edlinger@hotmail.de>
* c-lex.c (get_fileinfo): Use splay_tree_compare_strings and

4
gcc/c-family/c.opt
View File

@ -608,6 +608,10 @@ Winit-self
C ObjC C++ ObjC++ Var(warn_init_self) Warning LangEnabledBy(C++ ObjC++,Wall)
Warn about variables which are initialized to themselves.
Winit-list-lifetime
C++ ObjC++ Var(warn_init_list) Warning Init(1)
Warn about uses of std::initializer_list that can result in dangling pointers.
Wimplicit
C ObjC Var(warn_implicit) Warning LangEnabledBy(C ObjC,Wall)
Warn about implicit declarations.

14
gcc/cp/ChangeLog
View File

@ -1,3 +1,17 @@
2018-05-29 Jason Merrill <jason@redhat.com>
PR c++/67445 - returning temporary initializer_list.
PR c++/67711 - assigning from temporary initializer_list.
PR c++/48562 - new initializer_list.
* typeck.c (maybe_warn_about_returning_address_of_local): Also warn
about returning local initializer_list.
* cp-tree.h (AUTO_TEMP_NAME, TEMP_NAME_P): Remove.
* call.c (build_over_call): Warn about assignment from temporary
init_list.
* init.c (build_new_1): Warn about 'new std::initializer_list'.
(find_list_begin, maybe_warn_list_ctor): New.
(perform_member_init): Use maybe_warn_list_ctor.
2018-05-29 Marek Polacek <polacek@redhat.com>
PR c++/85883

6
gcc/cp/call.c
View File

@ -8217,6 +8217,7 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
tree type = TREE_TYPE (to);
tree as_base = CLASSTYPE_AS_BASE (type);
tree arg = argarray[1];
location_t loc = EXPR_LOC_OR_LOC (arg, input_location);
if (is_really_empty_class (type))
{
@ -8226,6 +8227,11 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
}
else if (tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (as_base)))
{
if (is_std_init_list (type)
&& conv_binds_ref_to_prvalue (convs[1]))
warning_at (loc, OPT_Winit_list_lifetime,
"assignment from temporary initializer_list does not "
"extend the lifetime of the underlying array");
arg = cp_build_fold_indirect_ref (arg);
val = build2 (MODIFY_EXPR, TREE_TYPE (to), to, arg);
}

7
gcc/cp/cp-tree.h
View File

@ -5234,10 +5234,6 @@ extern GTY(()) vec<tree, va_gc> *keyed_classes;
#else /* NO_DOLLAR_IN_LABEL */
#define AUTO_TEMP_NAME "__tmp_"
#define TEMP_NAME_P(ID_NODE) \
(!strncmp (IDENTIFIER_POINTER (ID_NODE), AUTO_TEMP_NAME, \
sizeof (AUTO_TEMP_NAME) - 1))
#define VTABLE_NAME "__vt_"
#define VTABLE_NAME_P(ID_NODE) \
(!strncmp (IDENTIFIER_POINTER (ID_NODE), VTABLE_NAME, \
@ -5272,8 +5268,6 @@ extern GTY(()) vec<tree, va_gc> *keyed_classes;
&& IDENTIFIER_POINTER (ID_NODE)[2] == 't' \
&& IDENTIFIER_POINTER (ID_NODE)[3] == JOINER)
#define TEMP_NAME_P(ID_NODE) \
(!strncmp (IDENTIFIER_POINTER (ID_NODE), AUTO_TEMP_NAME, sizeof (AUTO_TEMP_NAME)-1))
#define VFIELD_NAME_P(ID_NODE) \
(!strncmp (IDENTIFIER_POINTER (ID_NODE), VFIELD_NAME, sizeof(VFIELD_NAME)-1))
@ -6888,6 +6882,7 @@ extern void finish_label_decl (tree);
extern cp_expr finish_parenthesized_expr (cp_expr);
extern tree force_paren_expr (tree);
extern tree maybe_undo_parenthesized_ref (tree);
extern tree maybe_strip_ref_conversion (tree);
extern tree finish_non_static_data_member (tree, tree, tree);
extern tree begin_stmt_expr (void);
extern tree finish_stmt_expr_expr (tree, tree);

65
gcc/cp/init.c
View File

@ -674,6 +674,64 @@ maybe_reject_flexarray_init (tree member, tree init)
return true;
}
/* If INIT's value can come from a call to std::initializer_list<T>::begin,
return that function. Otherwise, NULL_TREE. */
static tree
find_list_begin (tree init)
{
STRIP_NOPS (init);
while (TREE_CODE (init) == COMPOUND_EXPR)
init = TREE_OPERAND (init, 1);
STRIP_NOPS (init);
if (TREE_CODE (init) == COND_EXPR)
{
tree left = TREE_OPERAND (init, 1);
if (!left)
left = TREE_OPERAND (init, 0);
left = find_list_begin (left);
if (left)
return left;
return find_list_begin (TREE_OPERAND (init, 2));
}
if (TREE_CODE (init) == CALL_EXPR)
if (tree fn = get_callee_fndecl (init))
if (id_equal (DECL_NAME (fn), "begin")
&& is_std_init_list (DECL_CONTEXT (fn)))
return fn;
return NULL_TREE;
}
/* If INIT initializing MEMBER is copying the address of the underlying array
of an initializer_list, warn. */
static void
maybe_warn_list_ctor (tree member, tree init)
{
tree memtype = TREE_TYPE (member);
if (!init || !TYPE_PTR_P (memtype)
|| !is_list_ctor (current_function_decl))
return;
tree parms = FUNCTION_FIRST_USER_PARMTYPE (current_function_decl);
tree initlist = non_reference (TREE_VALUE (parms));
tree targs = CLASSTYPE_TI_ARGS (initlist);
tree elttype = TREE_VEC_ELT (targs, 0);
if (!same_type_ignoring_top_level_qualifiers_p
(TREE_TYPE (memtype), elttype))
return;
tree begin = find_list_begin (init);
if (!begin)
return;
location_t loc = EXPR_LOC_OR_LOC (init, input_location);
warning_at (loc, OPT_Winit_list_lifetime,
"initializing %qD from %qE does not extend the lifetime "
"of the underlying array", member, begin);
}
/* Initialize MEMBER, a FIELD_DECL, with INIT, a TREE_LIST of
arguments. If TREE_LIST is void_type_node, an empty initializer
list was given; if NULL_TREE no initializer was given. */
@ -886,6 +944,8 @@ perform_member_init (tree member, tree init)
init = build_x_compound_expr_from_list (init, ELK_MEM_INIT,
tf_warning_or_error);
maybe_warn_list_ctor (member, init);
/* Reject a member initializer for a flexible array member. */
if (init && !maybe_reject_flexarray_init (member, init))
finish_expr_stmt (cp_build_modify_expr (input_location, decl,
@ -2934,6 +2994,11 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
return error_mark_node;
}
if (is_std_init_list (elt_type))
warning (OPT_Winit_list_lifetime,
"%<new%> of initializer_list does not "
"extend the lifetime of the underlying array");
if (abstract_virtuals_error_sfinae (ACU_NEW, elt_type, complain))
return error_mark_node;

71
gcc/cp/typeck.c
View File

@ -9012,6 +9012,7 @@ maybe_warn_about_returning_address_of_local (tree retval)
{
tree valtype = TREE_TYPE (DECL_RESULT (current_function_decl));
tree whats_returned = fold_for_warn (retval);
location_t loc = EXPR_LOC_OR_LOC (retval, input_location);
for (;;)
{
@ -9024,6 +9025,21 @@ maybe_warn_about_returning_address_of_local (tree retval)
break;
}
if (TREE_CODE (whats_returned) == TARGET_EXPR
&& is_std_init_list (TREE_TYPE (whats_returned)))
{
tree init = TARGET_EXPR_INITIAL (whats_returned);
if (TREE_CODE (init) == CONSTRUCTOR)
/* Pull out the array address. */
whats_returned = CONSTRUCTOR_ELT (init, 0)->value;
else if (TREE_CODE (init) == INDIRECT_REF)
/* The source of a trivial copy looks like *(T*)&var. */
whats_returned = TREE_OPERAND (init, 0);
else
return false;
STRIP_NOPS (whats_returned);
}
if (TREE_CODE (whats_returned) != ADDR_EXPR)
return false;
whats_returned = TREE_OPERAND (whats_returned, 0);
@ -9032,21 +9048,17 @@ maybe_warn_about_returning_address_of_local (tree retval)
|| TREE_CODE (whats_returned) == ARRAY_REF)
whats_returned = TREE_OPERAND (whats_returned, 0);
if (TYPE_REF_P (valtype))
if (TREE_CODE (whats_returned) == AGGR_INIT_EXPR
|| TREE_CODE (whats_returned) == TARGET_EXPR)
{
if (TREE_CODE (whats_returned) == AGGR_INIT_EXPR
|| TREE_CODE (whats_returned) == TARGET_EXPR)
{
warning (OPT_Wreturn_local_addr, "returning reference to temporary");
return true;
}
if (VAR_P (whats_returned)
&& DECL_NAME (whats_returned)
&& TEMP_NAME_P (DECL_NAME (whats_returned)))
{
warning (OPT_Wreturn_local_addr, "reference to non-lvalue returned");
return true;
}
if (TYPE_REF_P (valtype))
warning_at (loc, OPT_Wreturn_local_addr,
"returning reference to temporary");
else if (is_std_init_list (valtype))
warning_at (loc, OPT_Winit_list_lifetime,
"returning temporary initializer_list does not extend "
"the lifetime of the underlying array");
return true;
}
if (DECL_P (whats_returned)
@ -9056,19 +9068,27 @@ maybe_warn_about_returning_address_of_local (tree retval)
&& !(TREE_STATIC (whats_returned)
|| TREE_PUBLIC (whats_returned)))
{
bool w = false;
if (TYPE_REF_P (valtype))
warning_at (DECL_SOURCE_LOCATION (whats_returned),
OPT_Wreturn_local_addr,
"reference to local variable %qD returned",
whats_returned);
w = warning_at (loc, OPT_Wreturn_local_addr,
"reference to local variable %qD returned",
whats_returned);
else if (is_std_init_list (valtype))
w = warning_at (loc, OPT_Winit_list_lifetime,
"returning local initializer_list variable %qD "
"does not extend the lifetime of the underlying array",
whats_returned);
else if (TREE_CODE (whats_returned) == LABEL_DECL)
warning_at (DECL_SOURCE_LOCATION (whats_returned),
OPT_Wreturn_local_addr, "address of label %qD returned",
whats_returned);
w = warning_at (loc, OPT_Wreturn_local_addr,
"address of label %qD returned",
whats_returned);
else
warning_at (DECL_SOURCE_LOCATION (whats_returned),
OPT_Wreturn_local_addr, "address of local variable %qD "
"returned", whats_returned);
w = warning_at (loc, OPT_Wreturn_local_addr,
"address of local variable %qD returned",
whats_returned);
if (w)
inform (DECL_SOURCE_LOCATION (whats_returned),
"declared here");
return true;
}
@ -9402,7 +9422,8 @@ check_return_expr (tree retval, bool *no_warning)
retval = build2 (COMPOUND_EXPR, TREE_TYPE (retval), retval,
TREE_OPERAND (retval, 0));
else if (!processing_template_decl
&& maybe_warn_about_returning_address_of_local (retval))
&& maybe_warn_about_returning_address_of_local (retval)
&& INDIRECT_TYPE_P (valtype))
retval = build2 (COMPOUND_EXPR, TREE_TYPE (retval), retval,
build_zero_cst (TREE_TYPE (retval)));
}

45
gcc/doc/invoke.texi
View File

@ -2909,6 +2909,51 @@ assignment operator is deprecated if the class has a user-provided
copy constructor, copy assignment operator, or destructor, in C++11
and up. This warning is enabled by @option{-Wall}.
@item -Wno-init-list-lifetime @r{(C++ and Objective-C++ only)}
@opindex Winit-list-lifetime
@opindex Wno-init-list-lifetime
Do not warn about uses of @code{std::initializer_list} that are likely
to result in dangling pointers. Since the underlying array for an
@code{initializer_list} is handled like a normal C++ temporary object,
it is easy to inadvertently keep a pointer to the array past the end
of the array's lifetime. For example:
@itemize @bullet
@item
If a function returns a temporary @code{initializer_list}, or a local
@code{initializer_list} variable, the array's lifetime ends at the end
of the return statement, so the value returned has a dangling pointer.
@item
If a new-expression creates an @code{initializer_list}, the array only
lives until the end of the enclosing full-expression, so the
@code{initializer_list} in the heap has a dangling pointer.
@item
When an @code{initializer_list} variable is assigned from a
brace-enclosed initializer list, the temporary array created for the
right side of the assignment only lives until the end of the
full-expression, so at the next statement the @code{initializer_list}
variable has a dangling pointer.
@smallexample
// li's initial underlying array lives as long as li
std::initializer_list<int> li = @{ 1,2,3 @};
// assignment changes li to point to a temporary array
li = @{ 4, 5 @};
// now the temporary is gone and li has a dangling pointer
int i = li.begin()[0] // undefined behavior
@end smallexample
@item
When a list constructor stores the @code{begin} pointer from the
@code{initializer_list} argument, this doesn't extend the lifetime of
the array, so if a class variable is constructed from a temporary
@code{initializer_list}, the pointer is left dangling by the end of
the variable declaration statement.
@end itemize
@item -Wliteral-suffix @r{(C++ and Objective-C++ only)}
@opindex Wliteral-suffix
@opindex Wno-literal-suffix

15
gcc/testsuite/c-c++-common/pr43395.c
View File

@ -5,27 +5,24 @@
void *
foo (void)
{
lab: /* { dg-line foo_lab } */
lab:
return &&lab;
/* { dg-warning "function returns address of label" "" { target c } .-1 } */
/* { dg-warning "address of label" "" { target c++ } foo_lab } */
/* { dg-warning "address of label" "" { target *-*-* } .-1 } */
}
void *
bar (void)
{
__label__ lab;
lab: /* { dg-line bar_lab } */
lab:
return &&lab;
/* { dg-warning "function returns address of label" "" { target c } .-1 } */
/* { dg-warning "address of label" "" { target c++ } bar_lab } */
/* { dg-warning "address of label" "" { target *-*-* } .-1 } */
}
void *
baz (void)
{
int i; /* { dg-line baz_i } */
int i;
return &i;
/* { dg-warning "function returns address of local variable" "" { target c } .-1 } */
/* { dg-warning "address of local variable" "" { target c++ } baz_i } */
/* { dg-warning "address of local variable" "" { target *-*-* } .-1 } */
}

8
gcc/testsuite/g++.dg/cpp1y/pr77591.C
View File

@ -7,13 +7,13 @@ class A { };
decltype(auto)
foo ()
{
A c; // { dg-warning "reference to local variable 'c' returned" }
return (c);
A c;
return (c); // { dg-warning "reference to local variable 'c' returned" }
}
decltype(auto)
bar ()
{
A c; // { dg-warning "reference to local variable 'c' returned" }
return 1==1 ? c : c;
A c;
return 1==1 ? c : c; // { dg-warning "reference to local variable 'c' returned" }
}

15
gcc/testsuite/g++.dg/warn/Winit-list1.C Normal file
View File

@ -0,0 +1,15 @@
// PR c++/67711, 48562
// { dg-do compile { target c++11 } }
#include <initializer_list>
using IL = std::initializer_list<int>;
int main()
{
IL il = { 1,2,3 };
il = { 4,5,6 }; // { dg-warning "initializer_list" }
// the array is dead, il now points to garbage
il = *new IL{ 7, 8, 9 }; // { dg-warning "initializer_list" }
// the array is dead, il now points to garbage
return *il.begin(); // undefined
}

32
gcc/testsuite/g++.dg/warn/Winit-list2.C Normal file
View File

@ -0,0 +1,32 @@
// { dg-do compile { target c++11 } }
#include <initializer_list>
extern "C" int printf (const char *, ...);
using size_t = decltype(sizeof(0));
template <typename T> class ArrayRef {
public:
using size_type = size_t;
private:
/// The start of the array, in an external buffer.
const T *Data = nullptr;
/// The number of elements.
size_type Length = 0;
public:
/// Construct an ArrayRef from a std::initializer_list.
/*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
: Data(Vec.begin() == Vec.end() ? (T *)nullptr : Vec.begin()), // { dg-warning initializer_list }
Length(Vec.size()) {}
const T &operator[](size_t Index) const { return Data[Index]; }
};
int main() {
const ArrayRef<int> Foo = {42};
printf ("Foo %d\n", Foo[0]);
}

34
gcc/testsuite/g++.dg/warn/Winit-list3.C Normal file
View File

@ -0,0 +1,34 @@
// PR c++/67445
// { dg-do compile { target c++11 } }
#include <initializer_list>
using SL = std::initializer_list<char const*>;
SL retArray(int i) noexcept
{
if (i == 0)
{
SL l{"Test 1", "Test 2", "Test 3"}; // { dg-message "declared" }
return l; // { dg-warning "initializer_list" }
}
else if (i == 1)
return SL{"Test 1", "Test 2", "Test 3"}; // { dg-warning "initializer_list" }
else if (i == 2)
return {"Test 1", "Test 2", "Test 3"}; // { dg-warning "initializer_list" }
else
{
static SL l{"Test 1", "Test 2", "Test 3"};
return l; // no warning about returning static.
}
}
const char *p;
int main(int, char const* const*)
{
for (auto&& i : retArray(1))
{
p = i;
}
return 0;
}

8
gcc/testsuite/g++.dg/warn/Wreturn-local-addr.C
View File

@ -4,14 +4,14 @@
int& bad1()
{
int x = 0; // { dg-error "reference to local variable" }
return x;
int x = 0;
return x; // { dg-error "reference to local variable" }
}
int* bad2()
{
int x = 0; // { dg-error "address of local variable" }
return &x;
int x = 0;
return &x; // { dg-error "address of local variable" }
}
const int& bad4()

8
gcc/testsuite/g++.dg/warn/return-reference2.C
View File

@ -10,12 +10,12 @@ public:
int &f()
{
A a; // { dg-warning "local" }
return a.second;
A a;
return a.second; // { dg-warning "local" }
}
int &g()
{
int ar[42]; // { dg-warning "local" }
return ar[20];
int ar[42];
return ar[20]; // { dg-warning "local" }
}

4
gcc/testsuite/g++.old-deja/g++.bob/array1.C
View File

@ -1,6 +1,6 @@
// { dg-do assemble }
char *stuff() {
char array[10]; // { dg-warning "" }
char array[10];
return array;
return array; // { dg-warning "" }
}

4
gcc/testsuite/g++.old-deja/g++.brendan/crash55.C
View File

@ -4,9 +4,9 @@
int& f(int x) // { dg-error "new declaration" }
{
int local; // { dg-warning "reference to local" }
int local;
local = x+2;
return local;
return local; // { dg-warning "reference to local" }
}

5
libstdc++-v3/testsuite/util/testsuite_random.h
View File

@ -113,7 +113,10 @@ namespace __gnu_test
discrete_pdf(int k, std::initializer_list<double> wl)
{
if (!wl.size())
wl = { 1.0 };
{
static std::initializer_list<double> one = { 1.0 };
wl = one;
}
if (k < 0 || (std::size_t)k >= wl.size())
return 0.0;