Merge pull request #3616 from lethosor/check-structures-sanity-fix-string-cxx11

check-structures-sanity: update detection for GCC C++11 std::string

plugins/devel/check-structures-sanity/dispatch.cpp

@@ -1,5 +1,7 @@
 #include "check-structures-sanity.h"
 
+#include <cinttypes>
+
 #include "df/large_integer.h"
 
 Checker::Checker(color_ostream & out) :
@@ -845,69 +847,51 @@ void Checker::check_stl_string(const QueueItem & item)
 #else
     struct string_data
     {
-        struct string_data_inner
+        uintptr_t start;
+        size_t length;
+        union
         {
-            size_t length;
+            char local_data[16];
             size_t capacity;
-            int32_t refcount;
+        };
-        } *ptr;
     };
 #endif
 
     auto string = reinterpret_cast<const string_data *>(item.ptr);
 #ifdef WIN32
-    bool is_local = string->capacity < 16;
+    const bool is_gcc = false;
+    const bool is_local = string->capacity < 16;
+#else
+    const bool is_gcc = true;
+    const bool is_local = string->start == reinterpret_cast<uintptr_t>(&string->local_data[0]);
+#endif
     const char *start = is_local ? &string->local_data[0] : reinterpret_cast<const char *>(string->start);
     ptrdiff_t length = string->length;
     ptrdiff_t capacity = string->capacity;
-#else
+
-    if (!is_valid_dereference(QueueItem(item, "?ptr?", string->ptr), 1))
+    (void)start;
+    if (length < 0)
     {
-        // nullptr is NOT okay here
+        FAIL("string length is negative (" << length << ")");
-        FAIL("invalid string pointer " << stl_sprintf("%p", string->ptr));
-        return;
     }
-    if (!is_valid_dereference(QueueItem(item, "?hdr?", string->ptr - 1), sizeof(*string->ptr)))
+    else if (is_gcc && length > 0 && !is_valid_dereference(QueueItem(item, "?start?", reinterpret_cast<void *>(string->start)), 1))
     {
+        // nullptr is NOT okay here
+        FAIL("invalid string pointer " << stl_sprintf("0x%" PRIxPTR, string->start));
         return;
     }
-    const char *start = reinterpret_cast<const char *>(string->ptr);
+    else if (is_local && length >= 16)
-    ptrdiff_t length = (string->ptr - 1)->length;
-    ptrdiff_t capacity = (string->ptr - 1)->capacity;
-#endif
-
-    (void)start;
-    if (length < 0)
     {
-        FAIL("string length is negative (" << length << ")");
+        FAIL("string length is too large for small string (" << length << ")");
     }
-    else if (capacity < 0)
+    else if ((!is_gcc || !is_local) && capacity < 0)
     {
         FAIL("string capacity is negative (" << capacity << ")");
     }
-    else if (capacity < length)
+    else if ((!is_gcc || !is_local) && capacity < length)
     {
         FAIL("string capacity (" << capacity << ") is less than length (" << length << ")");
     }
-
-#ifndef WIN32
-    const std::string empty_string;
-    auto empty_string_data = reinterpret_cast<const string_data *>(&empty_string);
-    if (sizes && string->ptr != empty_string_data->ptr)
-    {
-        size_t allocated_size = get_allocated_size(QueueItem(item, "?hdr?", string->ptr - 1));
-        size_t expected_size = sizeof(*string->ptr) + capacity + 1;
-
-        if (!allocated_size)
-        {
-            FAIL("pointer does not appear to be a string");
-        }
-        else if (allocated_size != expected_size)
-        {
-            FAIL("allocated string data size (" << allocated_size << ") does not match expected size (" << expected_size << ")");
-        }
-    }
-#endif
 }
 void Checker::check_possible_pointer(const QueueItem & item, const CheckedStructure & cs)
 {