PR middle-end/91679 - missing -Warray-bounds accessing a member array in a local buffer

PR middle-end/91679 - missing -Warray-bounds accessing a member array in a local buffer
PR middle-end/91647 - new FAILs for Warray-bounds-8 and Wstringop-overflow-3.C
PR middle-end/91463 - missing -Warray-bounds accessing past the end of a statically initialized flexible array member
PR middle-end/92312 - bogus -Wstringop-overflow storing into a trailing array backed by larger buffer

gcc/ChangeLog:

	PR middle-end/91679
	PR middle-end/91647
	PR middle-end/91463
	PR middle-end/92312
	* c-family/c-pretty-print.c (direct_abstract_declarator): Print
	bound in zero-length arrays.
	* gcc/c-family/c.opt (-Wzero-length-bounds): New option.
	* gcc/doc/invoke.texi (-Wzero-length-bounds): Document.
	* gimple-match-head.c (try_conditional_simplification): Use memcpy
	instead of a hand-rolled loop to avoid PR 92323.
	* tree-vrp.c (vrp_prop::check_array_ref): Handle trailing arrays
	with initializers.
	(vrp_prop::check_mem_ref): Handle declared struct objects.
	* tree.c (last_field): New function.
	(array_at_struct_end_p): Handle MEM_REF.
	(get_initializer_for): New helper.
	(component_ref_size): Add argument.  Rename locals.  Call
	get_initializer_for instead of fold_ctor_reference.  Correct handling
	of flexible array members.
	* wide-int.h (generic_wide_int <storage>::sign_mask): Assert invariant.

gcc/testsuite/ChangeLog:

	PR middle-end/91679
	PR middle-end/91647
	PR middle-end/91463
	PR middle-end/92312
	* c-c++-common/Warray-bounds-2.c: Disable VRP.  Adjust expected messages.
	* g++.dg/warn/Warray-bounds-8.C: Remove xfails.
	* gcc.dg/Warray-bounds-48.c: New test.
	* gcc.dg/Warray-bounds-49.c: New test.
	* gcc.dg/Wstringop-overflow-16.c: Adjust text of expected messages.
	* gcc.dg/Wstringop-overflow-21.c: New test.
	* gcc.dg/Wzero-length-array-bounds.c: New test.
	* gcc.dg/pr36902.c: Remove xfail.
	* gcc.dg/strlenopt-57.c: Add an expected warning.

From-SVN: r277728

1 files changed, 29 insertions, 0 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index d1eb317..faa7fa9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -325,6 +325,7 @@ Objective-C and Objective-C++ Dialects}.
 -Winaccessible-base @gol
 -Winit-self  -Winline  -Wno-int-conversion  -Wint-in-bool-context @gol
 -Wno-int-to-pointer-cast  -Winvalid-memory-model  -Wno-invalid-offsetof @gol
+-Wzero-length-bounds @gol
 -Winvalid-pch  -Wlarger-than=@var{byte-size} @gol
 -Wlogical-op  -Wlogical-not-parentheses  -Wlong-long @gol
 -Wmain  -Wmaybe-uninitialized  -Wmemset-elt-size  -Wmemset-transposed-args @gol
@@ -4438,6 +4439,7 @@ Options} and @ref{Objective-C and Objective-C++ Dialect Options}.
 -Wimplicit-int @r{(C and Objective-C only)} @gol
 -Wimplicit-function-declaration @r{(C and Objective-C only)} @gol
 -Winit-self @r{(only for C++)} @gol
+-Wzero-length-bounds @gol
 -Wlogical-not-parentheses @gol
 -Wmain @r{(only for C/ObjC and unless} @option{-ffreestanding}@r{)}  @gol
 -Wmaybe-uninitialized @gol
@@ -6330,6 +6332,33 @@ conversions.  This warning is about implicit conversions; for explicit
 conversions the warnings @option{-Wno-int-to-pointer-cast} and
 @option{-Wno-pointer-to-int-cast} may be used.
 
+@item -Wzero-length-bounds
+@opindex Wzero-length-bounds
+@opindex Wzero-length-bounds
+Warn about accesses to elements of zero-length array members that might
+overlap other members of the same object.  Declaring interior zero-length
+arrays is discouraged because accesses to them are undefined.  See
+@xref{Zero Length}.
+
+For example, the first two stores in function @code{bad} are diagnosed
+because the array elements overlap the subsequent members @code{b} and
+@code{c}.  The third store is diagnosed by @option{-Warray-bounds}
+because it is beyond the bounds of the enclosing object.
+
+@smallexample
+struct X @{ int a[0]; int b, c; @};
+struct X x;
+
+void bad (void)
+@{
+  x.a[0] = 0;   // -Wzero-length-bounds
+  x.a[1] = 1;   // -Wzero-length-bounds
+  x.a[2] = 2;   // -Warray-bounds
+@}
+@end smallexample
+
+Option @option{-Wzero-length-bounds} is enabled by @option{-Warray-bounds}.
+
 @item -Wno-div-by-zero
 @opindex Wno-div-by-zero
 @opindex Wdiv-by-zero