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[C++ PATCH] Disable VLA initialization? (PR sanitizer/79993)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Wed, 29 Mar 2017 21:31:20 +0200
- Subject: [C++ PATCH] Disable VLA initialization? (PR sanitizer/79993)
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- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
GCC 4.8 and earlier didn't allow in C++ initialization of VLA and
C doesn't allow it in any GCC release. This has changed when the
support for C++1y VLA has been added, then reverted, but apparently
only partially.
The question is, do we want to support VLA initialization, if yes,
with what exact semantics (in that case we need to fix up initialization
from STRING_CST which is broken right now).
The following patch is the variant that disables it (bootstrapped/regtested
on x86_64-linux and i686-linux).
Looking at what is emitted for initialization from non-STRING_CSTs,
it seems that we consider UB if the VLA is shorter than the initializer
array, and if it is longer, we somehow initialize the rest (dunno what
exact C++ initialization kind, there are some testcases
with ctors in the list below; for PODs zero initialization).
So, if we want to keep it and just fix STRING_CST initialization,
shall we emit memcpy from the array followed by whatever we emit right now
for the excess elements (for initialization from STRING_CST, can it ever
be anything but zero initialization? If not, then memset would do the job).
2017-03-29 Jakub Jelinek <jakub@redhat.com>
PR sanitizer/79993
* decl.c (check_array_initializer): Reject VLA initialization.
* g++.dg/init/array24.C: Adjust for VLA initialization being
forbidden.
* g++.dg/opt/pr78201.C: Likewise.
* g++.dg/ubsan/vla-1.C: Likewise.
* g++.dg/ext/constexpr-vla1.C: Likewise.
* g++.dg/ext/constexpr-vla2.C: Likewise.
* g++.dg/ext/constexpr-vla3.C: Likewise.
* g++.dg/ext/constexpr-vla4.C: Likewise.
* g++.dg/cpp1y/pr63996.C: Likewise.
* g++.dg/cpp1y/vla-initlist1.C: Likewise.
* g++.dg/cpp1y/vla2.C: Likewise.
* g++.dg/cpp1y/vla10.C: Likewise.
--- gcc/cp/decl.c.jj 2017-03-21 07:57:00.000000000 +0100
+++ gcc/cp/decl.c 2017-03-29 09:45:20.741094070 +0200
@@ -6148,12 +6148,16 @@ check_array_initializer (tree decl, tree
error ("elements of array %q#T have incomplete type", type);
return true;
}
- /* A compound literal can't have variable size. */
- if (init && !decl
+ /* It is not valid to initialize a VLA. */
+ if (init
&& ((COMPLETE_TYPE_P (type) && !TREE_CONSTANT (TYPE_SIZE (type)))
|| !TREE_CONSTANT (TYPE_SIZE (element_type))))
{
- error ("variable-sized compound literal");
+ if (decl)
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "variable-sized object %qD may not be initialized", decl);
+ else
+ error ("variable-sized compound literal");
return true;
}
return false;
--- gcc/testsuite/g++.dg/init/array24.C.jj 2016-04-14 21:17:01.000000000 +0200
+++ gcc/testsuite/g++.dg/init/array24.C 2017-03-29 15:20:03.593188437 +0200
@@ -3,5 +3,5 @@
void foo(int i)
{
- int x[][i] = { 0 };
-}
+ int x[][i] = { 0 }; // { dg-error "variable-sized object .x. may not be initialized" }
+} // { dg-error "storage size of .x. isn.t known" "" { target *-*-* } .-1 }
--- gcc/testsuite/g++.dg/opt/pr78201.C.jj 2016-11-17 18:08:39.000000000 +0100
+++ gcc/testsuite/g++.dg/opt/pr78201.C 2017-03-29 14:56:08.673071231 +0200
@@ -8,6 +8,6 @@ long e;
void
foo ()
{
- char a[e] = "";
+ char a[e] = ""; // { dg-error "variable-sized object 'a' may not be initialized" }
c && c->d();
}
--- gcc/testsuite/g++.dg/ubsan/vla-1.C.jj 2016-04-14 21:17:01.000000000 +0200
+++ gcc/testsuite/g++.dg/ubsan/vla-1.C 2017-03-29 14:59:31.477405607 +0200
@@ -1,9 +1,8 @@
-// { dg-do run }
+// { dg-do compile }
// { dg-options "-Wno-vla -fsanitize=undefined" }
-// { dg-output "index 1 out of bounds" }
void f(int i) {
- int ar[i] = { 42, 24 };
+ int ar[i] = { 42, 24 }; // { dg-error "variable-sized object .ar. may not be initialized" }
}
int main()
--- gcc/testsuite/g++.dg/ext/constexpr-vla2.C.jj 2016-04-04 12:28:40.000000000 +0200
+++ gcc/testsuite/g++.dg/ext/constexpr-vla2.C 2017-03-29 14:52:55.648624577 +0200
@@ -4,7 +4,7 @@
constexpr int
fn_bad (int n)
{
- __extension__ int a [n] = { 0 };
+ __extension__ int a [n] = { 0 }; // { dg-error "variable-sized object .a. may not be initialized" }
int z = a [0] + (n ? fn_bad (n - 1) : 0);
return z;
}
@@ -12,10 +12,10 @@ fn_bad (int n)
constexpr int
fn_ok (int n)
{
- __extension__ int a [n] = { 0 };
+ __extension__ int a [n] = { 0 }; // { dg-error "variable-sized object .a. may not be initialized" }
int z = a [0] + (n > 1 ? fn_ok (n - 1) : 0);
return z;
}
-constexpr int i1 = fn_ok (3);
-constexpr int i2 = fn_bad (3); // { dg-error "array subscript" }
+constexpr int i1 = fn_ok (3); // { dg-error "accessing uninitialized array element" }
+constexpr int i2 = fn_bad (3); // { dg-error "accessing uninitialized array element" }
--- gcc/testsuite/g++.dg/ext/constexpr-vla3.C.jj 2016-04-04 12:28:40.000000000 +0200
+++ gcc/testsuite/g++.dg/ext/constexpr-vla3.C 2017-03-29 14:53:52.174880426 +0200
@@ -4,11 +4,11 @@
constexpr int
foo (int n)
{
- __extension__ int a[n] = { 1, 2, 3, 4, 5, 6 };
+ __extension__ int a[n] = { 1, 2, 3, 4, 5, 6 }; // { dg-error "variable-sized object .a. may not be initialized" }
int z = 0;
for (int i = 0; i <= n; ++i)
z += a[i];
return z;
}
-constexpr int n = foo (3); // { dg-error "array subscript" }
+constexpr int n = foo (3); // { dg-error "accessing uninitialized array element" }
--- gcc/testsuite/g++.dg/ext/constexpr-vla1.C.jj 2016-04-04 12:28:40.000000000 +0200
+++ gcc/testsuite/g++.dg/ext/constexpr-vla1.C 2017-03-29 14:21:13.836697832 +0200
@@ -4,7 +4,7 @@
constexpr int
fn_ok (int n)
{
- __extension__ int a[n] = { };
+ __extension__ int a[n] = { }; // { dg-error "variable-sized object .a. may not be initialized" }
int z = 0;
for (unsigned i = 0; i < sizeof (a) / sizeof (int); ++i)
@@ -17,7 +17,7 @@ fn_ok (int n)
constexpr int
fn_not_ok (int n)
{
- __extension__ int a[n] = { };
+ __extension__ int a[n] = { }; // { dg-error "variable-sized object .a. may not be initialized" }
int z = 0;
for (unsigned i = 0; i < sizeof (a); ++i)
@@ -26,5 +26,5 @@ fn_not_ok (int n)
return z;
}
-constexpr int n1 = fn_ok (3);
-constexpr int n2 = fn_not_ok (3); // { dg-error "array subscript" }
+constexpr int n1 = fn_ok (3); // { dg-error "accessing uninitialized array element" }
+constexpr int n2 = fn_not_ok (3); // { dg-error "accessing uninitialized array element" }
--- gcc/testsuite/g++.dg/ext/constexpr-vla4.C.jj 2016-04-05 18:57:01.000000000 +0200
+++ gcc/testsuite/g++.dg/ext/constexpr-vla4.C 2017-03-29 14:54:54.589053166 +0200
@@ -4,7 +4,7 @@
constexpr int
foo (int n, bool p)
{
- __extension__ int a [n] = { 0 };
+ __extension__ int a [n] = { 0 }; // { dg-error "variable-sized object 'a' may not be initialized" }
if (n == 3)
foo (n - 2, false);
if (n == 3)
@@ -15,3 +15,4 @@ foo (int n, bool p)
}
constexpr int i2 = foo (3, false); // { dg-bogus "array subscript out of bound" }
+ // { dg-error "accessing uninitialized array element" "" { target *-*-* } .-1 }
--- gcc/testsuite/g++.dg/cpp1y/vla2.C.jj 2014-12-12 08:59:22.000000000 +0100
+++ gcc/testsuite/g++.dg/cpp1y/vla2.C 2017-03-29 14:18:47.996628357 +0200
@@ -1,10 +1,10 @@
// N3639 allows initialization and capture of VLAs
-// { dg-do run { target c++11 } }
+// { dg-do compile { target c++11 } }
// { dg-options "-Wno-vla" }
void f(int n)
{
- int ar[n] = { 42 };
+ int ar[n] = { 42 }; // { dg-error "variable-sized object 'ar' may not be initialized" }
auto l = [&] { return ar[0]; };
if (l() != 42) __builtin_abort ();
}
--- gcc/testsuite/g++.dg/cpp1y/vla-initlist1.C.jj 2017-02-09 12:59:40.000000000 +0100
+++ gcc/testsuite/g++.dg/cpp1y/vla-initlist1.C 2017-03-29 15:16:57.151656875 +0200
@@ -1,5 +1,4 @@
-// { dg-do run { target c++11 } }
-// { dg-skip-if "power overwrites two slots of array i" { "power*-*-*" } }
+// { dg-do compile { target c++11 } }
// { dg-options "-Wno-vla" }
#include <initializer_list>
@@ -15,9 +14,9 @@ struct A
int x = 4;
int main(int argc, char **argv)
{
- { int i[x] = { 42, 42, 42, 42 }; }
+ { int i[x] = { 42, 42, 42, 42 }; } // { dg-error "variable-sized object .i. may not be initialized" }
{
- A a[x] = { argc };
+ A a[x] = { argc }; // { dg-error "variable-sized object .a. may not be initialized" }
if (a[1].i != 42)
__builtin_abort ();
}
--- gcc/testsuite/g++.dg/cpp1y/pr63996.C.jj 2015-01-14 09:55:17.000000000 +0100
+++ gcc/testsuite/g++.dg/cpp1y/pr63996.C 2017-03-29 14:11:05.619748966 +0200
@@ -4,7 +4,7 @@ constexpr int
foo (int i)
{
int a[i] = { }; // { dg-error "forbids variable length" }
-}
+} // { dg-error "variable-sized object .a. may not be initialized" "" { target *-*-* } .-1 }
constexpr int j = foo (1); // { dg-error "flows off the end" }
--- gcc/testsuite/g++.dg/cpp1y/vla10.C.jj 2014-12-12 08:59:22.000000000 +0100
+++ gcc/testsuite/g++.dg/cpp1y/vla10.C 2017-03-29 14:17:39.552534370 +0200
@@ -1,5 +1,5 @@
// PR c++/57402
-// { dg-do run }
+// { dg-do compile }
// { dg-options "" }
int i = 2;
@@ -11,13 +11,13 @@ int main()
a[1] = 0xbeef;
}
{
- int a[i] = { 1 };
+ int a[i] = { 1 }; // { dg-error "variable-sized object .a. may not be initialized" }
if (a[1] != 0)
__builtin_abort ();
a[1] = 0xbeef;
}
{
- int a[i] = { };
+ int a[i] = { }; // { dg-error "variable-sized object .a. may not be initialized" }
if (a[1] != 0)
__builtin_abort ();
a[1] = 0xbeef;
Jakub