[PATCH] D38599: Remove warnings for dynamic_cast fallback.

[Dan Albert via Phabricator via cfe-commits]

danalbert created this revision.

This doesn't only happen for incorrectly built apps, it also happens
for libraries loaded with dlopen.


Repository:
  rL LLVM

https://reviews.llvm.org/D38599

Files:
  src/private_typeinfo.cpp


Index: src/private_typeinfo.cpp
===================================================================
--- src/private_typeinfo.cpp
+++ src/private_typeinfo.cpp
@@ -10,39 +10,19 @@
 #include "private_typeinfo.h"
 
 // The flag _LIBCXX_DYNAMIC_FALLBACK is used to make dynamic_cast more
-// forgiving when type_info's mistakenly have hidden visibility and thus
-// multiple type_infos can exist for a single type.
-// 
+// forgiving when multiple type_infos exist for a single type. This happens if
+// the libraries are mistakenly built with the type_infos having hidden
+// visibility, but also occurs when the libraries are loaded with dlopen.
+//
 // When _LIBCXX_DYNAMIC_FALLBACK is defined, and only in the case where
 // there is a detected inconsistency in the type_info hierarchy during a
 // dynamic_cast, then the equality operation will fall back to using strcmp
 // on type_info names to determine type_info equality.
-// 
-// This change happens *only* under dynamic_cast, and only when
-// dynamic_cast is faced with the choice:  abort, or possibly give back the
-// wrong answer.  If when the dynamic_cast is done with this fallback
-// algorithm and an inconsistency is still detected, dynamic_cast will call
-// abort with an appropriate message.
-// 
-// The current implementation of _LIBCXX_DYNAMIC_FALLBACK requires a
-// printf-like function called syslog:
-// 
-//     void syslog(int facility_priority, const char* format, ...);
-// 
-// If you want this functionality but your platform doesn't have syslog,
-// just implement it in terms of fprintf(stderr, ...).
-// 
+//
 // _LIBCXX_DYNAMIC_FALLBACK is currently off by default.
 
-
 #include <string.h>
 
-
-#ifdef _LIBCXX_DYNAMIC_FALLBACK
-#include "abort_message.h"
-#include <sys/syslog.h>
-#endif
-
 // On Windows, typeids are different between DLLs and EXEs, so comparing
 // type_info* will work for typeids from the same compiled file but fail
 // for typeids from a DLL and an executable. Among other things, exceptions
@@ -647,11 +627,11 @@
         //   find (static_ptr, static_type), either on a public or private path
         if (info.path_dst_ptr_to_static_ptr == unknown)
         {
-            // We get here only if there is some kind of visibility problem
-            //   in client code.
-            syslog(LOG_ERR, "dynamic_cast error 1: Both of the following type_info's "
-                    "should have public visibility.  At least one of them is hidden. %s" 
-                    ", %s.\n", static_type->name(), dynamic_type->name());
+            // We get here only if there is some kind of visibility problem in
+            // client code. Possibly because the binaries were built
+            // incorrectly, but possibly because the library was loaded with
+            // dlopen.
+            //
             // Redo the search comparing type_info's using strcmp
             info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
             info.number_of_dst_type = 1;
@@ -672,10 +652,6 @@
         if (info.path_dst_ptr_to_static_ptr == unknown &&
             info.path_dynamic_ptr_to_static_ptr == unknown)
         {
-            syslog(LOG_ERR, "dynamic_cast error 2: One or more of the following type_info's "
-                            " has hidden visibility.  They should all have public visibility.  "
-                            " %s, %s, %s.\n", static_type->name(), dynamic_type->name(),
-                    dst_type->name());
             // Redo the search comparing type_info's using strcmp
             info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
             dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, true);


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