PR c++/69517 - [5/6 regression] SEGV on a VLA with excess initializer elements

PR c++/69517 - [5/6 regression] SEGV on a VLA with excess initializer elements
PR c++/70019 - VLA size overflow not detected
PR c++/70588 - SIGBUS on a VLA larger than SIZE_MAX / 2

gcc/testsuite/ChangeLog:
2016-04-13  Martin Sebor  <msebor@redhat.com>

        PR c++/69517
        PR c++/70019
        PR c++/70588
        * c-c++-common/ubsan/vla-1.c (main): Catch exceptions.
        * g++.dg/cpp1y/vla11.C: New test.
        * g++.dg/cpp1y/vla12.C: New test.
        * g++.dg/cpp1y/vla13.C: New test.
        * g++.dg/cpp1y/vla14.C: New test.
        * g++.dg/cpp1y/vla3.C: Restore deleted test.
        * gcc/testsuite/g++.dg/init/array24.C: Fully brace VLA initializer.
        * g++.dg/ubsan/vla-1.C: Disable exceptions.

gcc/cp/ChangeLog:
2016-04-13  Martin Sebor  <msebor@redhat.com>

        PR c++/69517
        PR c++/70019
        PR c++/70588
        * cp-tree.h (throw_bad_array_length, build_vla_check): Declare new
        functions.
        * decl.c (check_initializer, cp_finish_decl): Call them.
        (reshape_init_r): Reject incompletely braced intializer-lists
        for VLAs.
        * init.c (throw_bad_array_length, build_vla_check)
        (build_vla_size_check, build_vla_init_check): Define new functions.
        * typeck2.c (split_nonconstant_init_1): Use variably_modified_type_p()
        to detect a VLA.
        (store_init_value): Same.

gcc/doc/ChangeLog:
2016-04-13  Martin Sebor  <msebor@redhat.com>

        PR c++/69517
        PR c++/70019
        PR c++/70588
        * extend.texi (Variable Length): Document C++ specifics.

libstdc++-v3/ChangeLog:
2016-04-13  Martin Sebor  <msebor@redhat.com>

        PR c++/69517
        * testsuite/25_algorithms/rotate/moveable2.cc: Make sure VLA
       upper bound is positive.

From-SVN: r234966

1 files changed, 36 insertions, 2 deletions

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index a5a8b23..6687d59 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -1638,14 +1638,48 @@ foo (int n)
 You can use the function @code{alloca} to get an effect much like
 variable-length arrays.  The function @code{alloca} is available in
 many other C implementations (but not in all).  On the other hand,
-variable-length arrays are more elegant.
+variable-length arrays are available in GCC for all targets and
+provide type safety.
 
 There are other differences between these two methods.  Space allocated
 with @code{alloca} exists until the containing @emph{function} returns.
 The space for a variable-length array is deallocated as soon as the array
 name's scope ends, unless you also use @code{alloca} in this scope.
 
-You can also use variable-length arrays as arguments to functions:
+Unlike GCC, G++ instruments variable-length arrays (@xref{Variable Length})
+with checks for erroneous uses: when a variable-length array object is
+created its runtime bounds are checked to detect non-positive values,
+integer overflows, sizes in excess of SIZE_MAX / 2 bytes, and excess
+initializers.  When an erroneous variable-length array is detected
+the runtime arranges for an exception to be thrown that matches a handler
+of type @code{std::bad_array_length}.
+
+Also unlike GCC, G++ allows variable-length arrays to be initialized.
+However, unlike initializer lists for ordinary multidimensional arrays,
+those for multidimensional variable-length arrays must be enclosed in
+pairs of curly braces delimiting each sequence of values to use to
+initialize each subarray.  Initializer lists that aren't unambiguously
+enclosed in braces are rejected with an error.  For example, in the
+following function, the initializer list for the ordinary @code{array}
+is accepted even though it isn't fully enclosed in braces.  The same
+initializer list, however, wouldn't be accepted for a multidimensional
+variable-length array.  To initialize the variable-length array @code{vla},
+the elements of the subarray @code{vla[m]} must be enclosed in braces
+as shown.  As with ordinary arrays, elements that aren't initialized
+explicitly are default-initialized.
+
+@smallexample
+void
+foo (int m, int n)
+@{
+  int array[2][3] = @{ 1, 2, 4, 5, 6 @};
+  int vla[m][n] = @{ @{ 1, 2 @}, @{ 4, 5, 6 @} @};
+@}
+@end smallexample
+
+
+In C programs (but not in C++) variable-length arrays can also be declared
+as function arguments:
 
 @smallexample
 struct entry