Compiler Warnings C4800 Through C4999
The latest version of this topic can be found at Compiler Warnings C4800 Through C4999.
The articles in this part of the documentation contain information about a subset of the Visual C++ compiler warnings. You can access the information here or, in the Output window in Visual Studio, you can select an error number and then press the F1 key.
In This Section
| Warning | Message |
|---|---|
| Compiler Warning (level 3) C4800 | 'type': forcing value to bool 'true' or 'false' (performance warning) |
| Compiler Warning C4801 | Return by reference is not verifiable: %s |
| Compiler Warning (level 1) C4803 | 'method': the raise method has a different storage class from that of the event, 'event' |
| Compiler Warning (level 1) C4804 | 'operation': unsafe use of type 'bool' in operation |
| Compiler Warning (level 1) C4805 | 'operation': unsafe mix of type 'type' and type 'type' in operation |
| Compiler warning (level 1) C4806 | 'operation': unsafe operation: no value of type 'type' promoted to type 'type' can equal the given constant |
| Compiler warning (level 1) C4807 | 'operation': unsafe mix of type 'type' and signed bit field of type 'type' |
| Compiler warning (level 1) C4808 | case 'value' is not a valid value for switch condition of type 'bool' |
| Compiler warning (level 1) C4809 | switch statement has redundant 'default' label; all possible 'case' labels are given |
| Compiler warning (level 1) C4810 | value of pragma pack(show) == n |
| Compiler warning (level 1) C4811 | value of pragma conform(forScope, show) == value |
| Compiler warning (level 1) C4812 | obsolete declaration style: please use 'new_syntax' instead |
| Compiler warning (level 1) C4813 | 'function': a friend function of a local class must have been previously declared |
| Compiler Warning (level 4) C4815 | 'var': zero-sized array in stack object will have no elements (unless the object is an aggregate that has been aggregate initialized) |
| Compiler warning (level 4) C4816 | 'param': parameter has a zero-sized array which will be truncated (unless the object is passed by reference) |
| Compiler warning (level 1) C4817 | 'member': illegal use of '.' to access this member; compiler replaced with '->' |
| Compiler Warning (level 1) C4819 | The file contains a character that cannot be represented in the current code page (number). Save the file in Unicode format to prevent data loss |
| Compiler Warning (level 4) C4820 | 'bytes' bytes padding added after construct 'member_name' |
| Compiler Warning (level 1) C4821 | Unable to determine Unicode encoding type, please save the file with signature (BOM) |
| Compiler warning (level 1) C4822 | 'member function': local class member function does not have a body |
| Compiler Warning (level 3) C4823 | 'function': uses pinning pointers but unwind semantics are not enabled. Consider using /EHa |
| Compiler warning (level 4) C4825 | |
| Compiler Warning (level 2) C4826 | Conversion from 'type1' to 'type_2' is sign-extended. This may cause unexpected runtime behavior. |
| Compiler warning (level 3) C4827 | A public 'ToString' method with 0 parameters should be marked as virtual and override |
| Compiler Warning (level 1) C4829 | Possibly incorrect parameters to function main. Consider 'int main(Platform::Array<Platform::String^>^ argv)' |
| Compiler Warning (level 1) C4835 | 'variable': the initializer for exported data will not be run until managed code is first executed in the host assembly |
| Compiler warning (level 4) C4837 | trigraph detected: 'trigraph' replaced by 'character' |
| Compiler Warning (level 1) C4838 | conversion from 'type_1' to 'type_2' requires a narrowing conversion |
| Compiler Warning C4867 | 'function': function call missing argument list; use 'call' to create a pointer to member |
| Compiler Warning C4868 | 'file(line_number)' compiler may not enforce left-to-right evaluation order in braced initialization list |
| Compiler warning (level 2) C4872 | floating point division by zero detected when compiling the call graph for the concurrency::parallel_for_each at: '%s' |
| Compiler warning (level 1) C4880 | casting from 'const type_1' to 'type_2': casting away constness from a pointer or reference may result in undefined behavior in an amp restricted function |
| Compiler warning (level 4) C4881 | the constructor and/or the destructor will not be invoked for tile_static variable 'variable' |
| Compiler warning (level 1) C4882 | passing functors with non-const call operators to concurrency::parallel_for_each is deprecated |
| Compiler warning C4900 | Il mismatch between 'tool1' version 'version1' and 'tool2' version 'version2' |
| Compiler Warning (level 1) C4905 | wide string literal cast to 'LPSTR' |
| Compiler Warning (level 1) C4906 | string literal cast to 'LPWSTR' |
| Compiler warning (level 1) C4910 | '<identifier>: '__declspec(dllexport)' and 'extern' are incompatible on an explicit instantiation |
| Compiler warning (level 1) C4912 | 'attribute': attribute has undefined behavior on a nested UDT |
| Compiler warning (level 4) C4913 | user defined binary operator ',' exists but no overload could convert all operands, default built-in binary operator ',' used |
| Compiler warning (level 1) C4916 | in order to have a dispid, '%$S': must be introduced by an interface |
| Compiler Warning (level 1) C4917 | 'declarator': a GUID can only be associated with a class, interface or namespace |
| Compiler warning (level 4) C4918 | 'character': invalid character in pragma optimization list |
| Compiler warning (level 1) C4920 | enum enum member member_1=value_1 already seen in enum enum as member_2=value_2 |
| Compiler warning (level 3) C4921 | '%s': attribute value '%s' should not be multiply specified |
| Compiler warning (level 1) C4925 | 'method': dispinterface method cannot be called from script |
| Compiler warning (level 1) C4926 | 'identifier': symbol is already defined: attributes ignored |
| Compiler Warning (level 1) C4927 | illegal conversion; more than one user-defined conversion has been implicitly applied |
| Compiler Warning (level 1) C4928 | illegal copy-initialization; more than one user-defined conversion has been implicitly applied |
| Compiler Warning (level 1) C4929 | 'file': typelibrary contains a union; ignoring the 'embedded_idl' qualifier |
| Compiler Warning (level 1) C4930 | 'prototype': prototyped function not called (was a variable definition intended?) |
| Compiler Warning (level 4) C4931 | we are assuming the type library was built for number-bit pointers |
| Compiler warning (level 4) C4932 | __identifier(identifier) and __identifier(identifier) are indistinguishable |
| Compiler warning (level 1) C4934 | '__delegate(multicast)' is deprecated, use '__delegate' instead |
| Compiler warning (level 1) C4935 | assembly access specifier modified from 'access' |
| Compiler warning (level 1) C4936 | this __declspec is supported only when compiled with /clr or /clr:pure |
| Compiler warning (level 4) C4937 | 'text1' and 'text2' are indistinguishable as arguments to 'directive' |
| Compiler warning (level 4) C4938 | 'var': Floating point reduction variable may cause inconsistent results under /fp:strict or #pragma fenv_access |
| Compiler warning C4939 | #pragma vtordisp is deprecated and will be removed in a future release of Visual C++ |
| Compiler warning (level 1) C4944 | 'symbol': cannot import symbol from 'assembly1': as 'symbol' already exists in the current scope |
| Compiler Warning (level 1) C4945 | 'symbol': cannot import symbol from 'assembly1': as 'symbol' has already been imported from another assembly 'assembly2' |
| Compiler Warning (level 1) C4946 | reinterpret_cast used between related classes: 'class1' and 'class2' |
| Compiler warning (level 1) C4947 | 'type_or_member': marked as obsolete |
| Compiler Warning (level 2) C4948 | return type of 'accessor' does not match the last parameter type of the corresponding setter |
| Compiler Warning (level 1 and level 4) C4949 | pragmas 'managed' and 'unmanaged' are meaningful only when compiled with '/clr[:option]' |
| Compiler warning (level 1) C4950 | 'type_or_member': marked as obsolete |
| Compiler warning C4951 | 'function' has been edited since profile data was collected, function profile data not used |
| Compiler warning C4952 | 'function': no profile data found in program database 'pgd_file' |
| Compiler warning C4953 | Inline 'function' has been edited since profile data was collected, profile data not used |
| Compiler warning C4954 | 'function': not profiled (contains __int64 switch expression) |
| Compiler warning C4955 | 'import2': import ignored; already imported from 'import1' |
| Compiler warning (level 1) C4956 | 'type': this type is not verifiable |
| Compiler warning (level 1) C4957 | 'cast': explicit cast from 'cast from' to 'cast_to' is not verifiable |
| Compiler warning (level 1) C4958 | 'operation': pointer arithmetic is not verifiable |
| Compiler warning (level 1) C4959 | cannot define unmanaged type 'type' in /clr:safe because accessing its members yields unverifiable code |
| Compiler warning C4960 | 'function' is too big to be profiled |
| Compiler warning C4961 | No profile data was merged into '.pgd file', profile-guided optimizations disabled |
| Compiler warning C4962 | 'function': Profile-guided optimizations disabled because optimizations caused profile data to become inconsistent |
| Compiler warning C4963 | %s': no profile data found; different compiler options were used in instrumented build |
| Compiler Warning (level 1) C4964 | No optimization options were specified; profile info will not be collected |
| Compiler Warning (level 1) C4965 | implicit box of integer 0; use nullptr or explicit cast |
| Compiler warning C4966 | '%s' has __code_seg annotation with unsupported segment name, annotation ignored |
| Compiler warning C4970 | delegate constructor: target object ignored since '%$pS' is static |
| Compiler warning (level 1) C4971 | Argument order: <target object>, <target function> for delegate constructor is deprecated, use <target function>, <target object=""> |
| Compiler warning (level 1) C4972 | Directly modifying or treating the result of an unbox operation as an lvalue is unverifiable |
| Compiler warning C4973 | '%$S': marked as deprecated |
| Compiler warning C4974 | '%$S': marked as deprecated |
| Compiler warning C4981 | Warbird: function '%$pD' marked as __forceinline not inlined because it contains exception semantics |
| Compiler warning (level 3) C4985 | symbol name': attributes not present on previous declaration. |
| Compiler Warning C4986 | '%$pS': exception specification does not match previous declaration |
| Compiler warning (level 4) C4987 | nonstandard extension used: 'throw (...)' |
| Compiler warning (level 4) C4988 | '%$S': variable declared outside class/function scope |
| Compiler warning C4989 | '%s': type has conflicting definitions. |
| Compiler warning C4990 | Warbird: %s |
| Compiler warning C4991 | Warbird: function '%$pD' marked as __forceinline not inlined because protection level of inlinee is greater than the parent |
| Compiler warning C4992 | Warbird: function '%$pD' marked as __forceinline not inlined because it contains inline assembly which cannot be protected |
| Compiler Warning (level 3) C4995 | 'function': name was marked as #pragma deprecated |
| Compiler Warning (level 3) C4996 | '%$pS': %$* |
| Compiler warning (level 1) C4997 | 'class': coclass does not implement a COM interface or pseudo-interface |
| Compiler warning (level 1) C4998 | EXPECTATION FAILED: %s(%d) |
| Compiler warning C4999 | UNKNOWN WARNING %$N Please choose the Technical Support command on the Visual C++ %$N Help menu, or open the Technical Support help file for more information |