Add support for detecting mismatched allocation/deallocation calls.

PR c++/90629 - Support for -Wmismatched-new-delete
PR middle-end/94527 - Add an __attribute__ that marks a function as freeing an object

gcc/ChangeLog:

	PR c++/90629
	PR middle-end/94527
	* builtins.c (access_ref::access_ref): Initialize new member.
	(compute_objsize): Use access_ref::deref.  Handle simple pointer
	assignment.
	(expand_builtin): Remove handling of the free built-in.
	(call_dealloc_argno): Same.
	(find_assignment_location): New function.
	(fndecl_alloc_p): Same.
	(gimple_call_alloc_p): Same.
	(call_dealloc_p): Same.
	(matching_alloc_calls_p): Same.
	(warn_dealloc_offset): Same.
	(maybe_emit_free_warning): Same.
	* builtins.h (struct access_ref): Declare new member.
	(maybe_emit_free_warning): Make extern.  Make use of access_ref.
	Handle -Wmismatched-new-delete.
	* calls.c (initialize_argument_information): Call
	maybe_emit_free_warning.
	* doc/extend.texi (attribute malloc): Update.
	* doc/invoke.texi (-Wfree-nonheap-object): Expand documentation.
	(-Wmismatched-new-delete): Document new option.
	(-Wmismatched-dealloc): Document new option.

gcc/c-family/ChangeLog:

	PR c++/90629
	PR middle-end/94527
	* c-attribs.c (handle_dealloc_attribute): New function.
	(handle_malloc_attribute): Handle argument forms of attribute.
	* c.opt (-Wmismatched-dealloc): New option.
	(-Wmismatched-new-delete): New option.

gcc/testsuite/ChangeLog:

	PR c++/90629
	PR middle-end/94527
	* g++.dg/asan/asan_test.cc: Fix a bug.
	* g++.dg/warn/delete-array-1.C: Add expected warning.
	* g++.old-deja/g++.other/delete2.C: Add expected warning.
	* g++.dg/warn/Wfree-nonheap-object-2.C: New test.
	* g++.dg/warn/Wfree-nonheap-object.C: New test.
	* g++.dg/warn/Wmismatched-new-delete.C: New test.
	* g++.dg/warn/Wmismatched-dealloc-2.C: New test.
	* g++.dg/warn/Wmismatched-dealloc.C: New test.
	* gcc.dg/Wmismatched-dealloc.c: New test.
	* gcc.dg/analyzer/malloc-1.c: Prune out expected warning.
	* gcc.dg/attr-malloc.c: New test.
	* gcc.dg/free-1.c: Adjust text of expected warning.
	* gcc.dg/free-2.c: Same.
	* gcc.dg/torture/pr71816.c: Prune out expected warning.
	* gcc.dg/tree-ssa/pr19831-2.c: Add an expected warning.
	* gcc.dg/Wfree-nonheap-object-2.c: New test.
	* gcc.dg/Wfree-nonheap-object-3.c: New test.
	* gcc.dg/Wfree-nonheap-object.c: New test.

libstdc++-v3/ChangeLog:

	* testsuite/ext/vstring/modifiers/clear/56166.cc: Suppress a false
	positive warning.

2 files changed, 140 insertions, 12 deletions

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 195bb21..4357615 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3233,20 +3233,63 @@ this reason the attribute is not allowed on types to annotate indirect
 calls.
 
 @item malloc
+@item malloc (@var{deallocator})
+@item malloc (@var{deallocator}, @var{ptr-index})
 @cindex @code{malloc} function attribute
 @cindex functions that behave like malloc
-This tells the compiler that a function is @code{malloc}-like, i.e.,
-that the pointer @var{P} returned by the function cannot alias any
+Attribute @code{malloc} indicates that a function is @code{malloc}-like,
+i.e., that the pointer @var{P} returned by the function cannot alias any
 other pointer valid when the function returns, and moreover no
 pointers to valid objects occur in any storage addressed by @var{P}.
 
-Using this attribute can improve optimization.  Compiler predicts
-that a function with the attribute returns non-null in most cases.
-Functions like
-@code{malloc} and @code{calloc} have this property because they return
-a pointer to uninitialized or zeroed-out storage.  However, functions
-like @code{realloc} do not have this property, as they can return a
-pointer to storage containing pointers.
+Independently, the form of the attribute with one or two arguments
+associates @code{deallocator} as a suitable deallocation function for
+pointers returned from the @code{malloc}-like function.  @var{ptr-index}
+denotes the positional argument to which when the pointer is passed in
+calls to @code{deallocator} has the effect of deallocating it.
+
+Using the attribute with no arguments is designed to improve optimization.
+The compiler predicts that a function with the attribute returns non-null
+in most cases.  Functions like @code{malloc} and @code{calloc} have this
+property because they return a pointer to uninitialized or zeroed-out
+storage.  However, functions like @code{realloc} do not have this property,
+as they may return pointers to storage containing pointers to existing
+objects.
+
+Associating a function with a @var{deallocator} helps detect calls to
+mismatched allocation and deallocation functions and diagnose them
+under the control of options such as @option{-Wmismatched-dealloc}.
+To indicate that an allocation function both satisifies the nonaliasing
+property and has a deallocator associated with it, both the plain form
+of the attribute and the one with the @var{deallocator} argument must
+be used.
+
+For example, besides stating that the functions return pointers that do
+not alias any others, the following declarations make the @code{fclose}
+and @code{frepen} functions suitable deallocators for pointers returned
+from all the functions that return them, and the @code{pclose} function
+as the only other suitable deallocator besides @code{freopen} for pointers
+returned from @code{popen}.  The deallocator functions must declared
+before they can be referenced in the attribute.
+
+@smallexample
+int   fclose (FILE*);
+FILE* freopen (const char*, const char*, FILE*);
+int   pclose (FILE*);
+
+__attribute__ ((malloc, malloc (fclose), malloc (freopen, 3)))
+  FILE* fdopen (int);
+__attribute__ ((malloc, malloc (fclose), malloc (freopen, 3)))
+  FILE* fopen (const char*, const char*);
+__attribute__ ((malloc, malloc (fclose), malloc (freopen, 3)))
+  FILE* fmemopen(void *, size_t, const char *);
+__attribute__ ((malloc, malloc (fclose), malloc (freopen, 3)))
+  FILE* freopen (const char*, const char*, FILE*);
+__attribute__ ((malloc, malloc (pclose), malloc (freopen, 3)))
+  FILE* popen (const char*, const char*);
+__attribute__ ((malloc, malloc (fclose), malloc (freopen, 3)))
+  FILE* tmpfile (void);
+@end smallexample
 
 @item no_icf
 @cindex @code{no_icf} function attribute
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 35cd3dc..615eae9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -242,7 +242,8 @@ in the following sections.
 -Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
 -Weffc++  -Wno-exceptions -Wextra-semi  -Wno-inaccessible-base @gol
 -Wno-inherited-variadic-ctor  -Wno-init-list-lifetime @gol
--Wno-invalid-offsetof  -Wno-literal-suffix  -Wmismatched-tags @gol
+-Wno-invalid-offsetof  -Wno-literal-suffix @gol
+-Wno-mismatched-new-delete -Wmismatched-tags @gol
 -Wmultiple-inheritance  -Wnamespaces  -Wnarrowing @gol
 -Wnoexcept  -Wnoexcept-type  -Wnon-virtual-dtor @gol
 -Wpessimizing-move  -Wno-placement-new  -Wplacement-new=@var{n} @gol
@@ -3859,6 +3860,40 @@ The warning is inactive inside a system header file, such as the STL, so
 one can still use the STL.  One may also instantiate or specialize
 templates.
 
+@item -Wno-mismatched-new-delete @r{(C++ and Objective-C++ only)}
+@opindex Wmismatched-new-delete
+@opindex Wno-mismatched-new-delete
+Warn for mismatches between calls to @code{operator new} or @code{operator
+delete} and the corresponding call to the allocation or deallocation function.
+This includes invocations of C++ @code{operator delete} with pointers
+returned from either mismatched forms of @code{operator new}, or from other
+functions that allocate objects for which the @code{operator delete} isn't
+a suitable deallocator, as well as calls to other deallocation functions
+with pointers returned from @code{operator new} for which the deallocation
+function isn't suitable.
+
+For example, the @code{delete} expression in the function below is diagnosed
+because it doesn't match the array form of the @code{new} expression
+the pointer argument was returned from.  Similarly, the call to @code{free}
+is also diagnosed.
+
+@smallexample
+void f ()
+@{
+  int *a = new int[n];
+  delete a;   // warning: mismatch in array forms of expressions
+
+  char *p = new char[n];
+  free (p);   // warning: mismatch between new and free
+@}
+@end smallexample
+
+The related option @option{-Wmismatched-dealloc} diagnoses mismatches
+involving allocation and deallocation functions other than @code{operator
+new} and @code{operator delete}.
+
+@option{-Wmismatched-new-delete} is enabled by default.
+
 @item -Wmismatched-tags @r{(C++ and Objective-C++ only)}
 @opindex Wmismatched-tags
 @opindex Wno-mismatched-tags
@@ -6287,6 +6322,41 @@ Ignoring the warning can result in poorly optimized code.
 disable the warning, but this is not recommended and should be done only
 when non-existent profile data is justified.
 
+@item -Wno-mismatched-dealloc
+@opindex Wmismatched-dealloc
+@opindex Wno-mismatched-dealloc
+
+Warn for calls to deallocation functions with pointer arguments returned
+from from allocations functions for which the former isn't a suitable
+deallocator.  A pair of functions can be associated as matching allocators
+and deallocators by use of attribute @code{malloc}.  Unless disabled by
+the @option{-fno-builtin} option the standard functions @code{calloc},
+@code{malloc}, @code{realloc}, and @code{free}, as well as the corresponding
+forms of C++ @code{operator new} and @code{operator delete} are implicitly
+associated as matching allocators and deallocators.  In the following
+example @code{mydealloc} is the deallocator for pointers returned from
+@code{myalloc}.
+
+@smallexample
+void mydealloc (void*);
+
+__attribute__ ((malloc (mydealloc, 1))) void*
+myalloc (size_t);
+
+void f (void)
+@{
+  void *p = myalloc (32);
+  // @dots{}use p@dots{}
+  free (p);   // warning: not a matching deallocator for myalloc
+  mydealloc (p);   // ok
+@}
+@end smallexample
+
+In C++, the related option @option{-Wmismatched-new-delete} diagnoses
+mismatches involving either @code{operator new} or @code{operator delete}.
+
+Option @option{-Wmismatched-dealloc} is enabled by default.
+
 @item -Wmultistatement-macros
 @opindex Wmultistatement-macros
 @opindex Wno-multistatement-macros
@@ -7778,8 +7848,23 @@ to @option{-Wframe-larger-than=}@samp{SIZE_MAX} or larger.
 @item -Wno-free-nonheap-object
 @opindex Wno-free-nonheap-object
 @opindex Wfree-nonheap-object
-Do not warn when attempting to free an object that was not allocated
-on the heap.
+Warn when attempting to deallocate an object that was either not allocated
+on the heap, or by using a pointer that was not returned from a prior call
+to the corresponding allocation function.  For example, because the call
+to @code{stpcpy} returns a pointer to the terminating nul character and
+not to the begginning of the object, the call to @code{free} below is
+diagnosed.
+
+@smallexample
+void f (char *p)
+@{
+  p = stpcpy (p, "abc");
+  // ...
+  free (p);   // warning
+@}
+@end smallexample
+
+@option{-Wfree-nonheap-object} is enabled by default.
 
 @item -Wstack-usage=@var{byte-size}
 @opindex Wstack-usage