Microsoft C/C++ compiler warnings C5200 through C5399

The articles in this section describe Microsoft C/C++ compiler warning messages C5200 through C5399.

Important

The Visual Studio compilers and build tools can report many kinds of errors and warnings. After an error or warning is found, the build tools may make assumptions about code intent and attempt to continue, so that more issues can be reported at the same time. If the tools make the wrong assumption, later errors or warnings may not apply to your project. When you correct issues in your project, always start with the first error or warning that's reported, and rebuild often. One fix may make many subsequent errors go away.

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Note

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Warning messages

Warning	Message
Compiler warning (level 1) C5200	feature 'feature-name' requires compiler flag 'option-name'
Compiler warning (level 1) C5201	a module declaration can appear only at the start of a translation unit unless a global module fragment is used
Compiler warning (level 1) C5202	a global module fragment can only contain preprocessor directives
Compiler warning (level 1) C5203	a parenthesized declarator name after 'explicit' will be considered an explicit-specifier in C++20
Compiler warning (level 3, off) C5204	'type-name': class has virtual functions, but its trivial destructor is not virtual; instances of objects derived from this class may not be destructed correctly
Compiler warning (level 4) C5205	delete of an abstract class 'type-name' that has a non-virtual destructor results in undefined behavior
Compiler warning (level 3) C5206	deduced return types for coroutines is a non-standard extension
Compiler warning (level 1) C5207	the simple requirement asserts the validity of expression 'e->id'. Did you mean '{ e } -> id'? You can suppress the warning using '{ e->id }'
Compiler warning (level 1) C5208	unnamed class used in typedef name cannot declare members other than non-static data members, member enumerations, or member classes
Compiler warning (level 1) C5209	the C++20 syntax for an init-capture has changed to '& ...opt identifier initializer'
Compiler warning (level 1) C5210	'name' is not a valid header unit reference; ignoring
Compiler warning (level 1) C5212	'name' is not a valid named reference; treating as reference to file
Compiler warning (level 1) C5213	'name' named reference is treated as a named partition but the name is not specified; treating as reference to file
Compiler warning (level 4, off) C5214	applying 'modifier' to an operand with a volatile qualified type is deprecated in C++20
Compiler warning (level 4, off) C5215	'name' a function parameter with a volatile qualified type is deprecated in C++20
Compiler warning (level 4, off) C5216	'name' a volatile qualified return type is deprecated in C++20
Compiler warning (level 4, off) C5217	a structured binding declaration that includes volatile is deprecated in C++20
Compiler warning (level 1) C5218	destroying delete may not behave as intended when non-conforming switches '/Zc:sizedDealloc-' or '/Zc:alignedNew-' are used
Compiler warning (level 2, off) C5219	implicit conversion from 'type-1' to 'type-2', possible loss of data
Compiler warning (level 4, off) C5220	'name': a non-static data member with a volatile qualified type no longer implies that compiler generated copy/move constructors and copy/move assignment operators are not trivial
Compiler warning (level 1) C5221	xfg::rename is deprecated.
Compiler warning (level 3) C5222	'attribute-name': all unscoped attribute names are reserved for future standardization
Compiler warning (level 3) C5223	all attribute names in the attribute namespace 'msvc' are reserved for the implementation
Compiler warning (level 3) C5224	all attribute names in the attribute namespace 'namespace-name' are reserved for future standardization
Compiler warning (level 1) C5225	'symbol': exported inline function defined in a private module fragment is a non-standard extension
Compiler warning (level 1) C5226	'symbol': exported template defined in private module fragment has no reachable instantiation
Compiler warning (level 4) C5227	nonstandard extension, resolved 'symbol' to 'value' which is not visible with /permissive- on.
Compiler warning (level 4) C5228	nonstandard extension, 'identifier' resolved to a member of a dependent base. This lookup is not allowed under /permissive-.
Compiler warning (level 4) C5229	nonstandard extension, the hidden friend function 'function-name' was found by name lookup which isn't allowed under /permissive-.
Compiler warning C5230	nonstandard extension, 'identifier' was resolved to 'symbol-1' under /permissive. Under /permissive- it would resolve to 'symbol-2'.
Compiler warning (level 3) C5231	the expression 'co_await promise.final_suspend()' must be non-throwing
Compiler warning (level 1) C5232	in C++20 this comparison calls 'name' recursively
Compiler warning (level 4, off) C5233	explicit lambda capture 'identifier' is not used
Compiler warning (level 1) C5234	file system error: 'filename' is not a valid header-name; ignoring
Compiler warning (level 1) C5235	JSON parse error: message; ignoring 'filename'
Compiler warning (level 1) C5236	JSON ill-formed: message; ignoring 'filename'
Compiler warning (level 1) C5237	cannot resolve header unit entry 'name' to a header file in 'filename'; ignoring entry
Compiler warning (level 1) C5238	file system error: cannot open 'filename' for reading; ignoring
Compiler warning (level 4) C5239	'symbol': potentially throwing function called from a function declared __declspec(nothrow). Undefined behavior may occur if an exception is thrown.
Compiler warning (level 4) C5240	'attribute-name': attribute is ignored in this syntactic position
Compiler warning (level 1) C5241	'/exportHeader' usage to lookup header-name is deprecated; prefer '/headerName:name value=filename'
Compiler warning (level 1) C5242	syntax error in pragma 'identifier'
Compiler warning (level 1, off) C5243	'type-name': using incomplete class 'class-name' can cause potential one definition rule violation due to ABI limitation
Compiler warning (level 1) C5244	'#include <filename>' in the purview of module 'module-name-1' appears erroneous. Consider moving that directive before the module declaration, or replace the textual inclusion with 'import <module-name-2>;'.
Compiler warning (level 4, off) C5245	'function': unreferenced function with internal linkage has been removed
Compiler warning (level 1, off) C5246	'member': the initialization of a subobject should be wrapped in braces
Compiler warning (level 1, off) C5247	section 'section-name' is reserved for C++ dynamic initialization. Manually creating the section will interfere with C++ dynamic initialization and may lead to undefined behavior
Compiler warning (level 1, off) C5248	section 'section-name' is reserved for C++ dynamic initialization. Variables manually put into the section may be optimized out and their order relative to compiler generated dynamic initializers is unspecified.
Compiler warning (level 1, off) C5249	'bitfield' of type 'enumeration_name' has named enumerators with values that cannot be represented in the given bit field width of 'bitfield_width'.
Compiler warning (level 3, off) C5250	'function_name': intrinsic function not declared.
Compiler warning (level 4, off) C5251	segment-name changed after including header
Compiler warning (level 4) C5252	Multiple different types resulted in the same XFG type-hash hash-value; the PDB will only record information for one of them
Compiler warning (level 4) C5253	a non-local lambda cannot have a capture default
Compiler warning (level 4, off) C5254	language feature 'terse static assert' requires compiler flag '/std:c++17'
Compiler warning (level 3) C5255	unterminated bidirectional character encountered: 'U+XXXX'
Compiler warning (level 1, off) C5256	'enumeration': a non-defining declaration of an enumeration with a fixed underlying type is only permitted as a standalone declaration
Compiler warning (level 1 or 4) C5257	'enumeration': enumeration was previously declared without a fixed underlying type
Compiler warning (level 4, off) C5258	explicit capture of 'symbol' is not required for this use
Compiler warning (level 4, off) C5259	'specialized-type': explicit specialization requires 'template <>'
Compiler warning (level 1) C5260	the constant variable 'variable-name' has internal linkage in an included header file context, but external linkage in imported header unit context; consider declaring it 'inline' as well if it will be shared across translation units, or 'static' to express intent to use it local to this translation unit
Compiler warning (level 2) C5261	no integer type can represent all enumerator values in enumeration 'enum-name'
Compiler warning (level 1, error, off) C5262	implicit fall-through occurs here; are you missing a break statement? Use [[fallthrough]] when a break statement is intentionally omitted between cases
Compiler warning (level 4, off) C5263	calling 'std::move' on a temporary object prevents copy elision
Compiler warning (level 4, off) C5264	'variable-name': 'const' variable is not used
Compiler warning (level 1) C5265	cannot open search path 'path'
Compiler warning (level 4, off) C5266	'const' qualifier on return type has no effect
Compiler warning C5267	definition of implicit copy constructor/assignment operator for 'type' is deprecated because it has a user-provided assignment operator/copy constructor
Compiler warning (level 1) C5268	Failed to allocate memory at fixed address 0xaddress. Use /Yb to specify a specific address base if bit-identical .pch files are required.
Compiler warning (level 1) C5269	Failed to allocate PCH memory at fixed address 0xaddress. Use /Ym to specify a specific address base if bit-identical .pch files are required.
Compiler warning (level 3) C5270	'value' is not allowed for option 'switch name'; allowed values are: value list
Compiler warning (level 4) C5271	previously imported assembly 'assembly1' has the same name as assembly 'assembly2' being imported. Is this intentional?
Compiler warning (level 1) C5272	throwing an object of non-copyable type 'type' is non-standard. If a copy is needed at runtime it will be made as if by memcpy.
Compiler warning (level 1) C5273	behavior change: _Alignas on anonymous type no longer ignored (promoted members will align)
Compiler warning (level 1) C5274	behavior change: _Alignas no longer applies to the type 'type' (only applies to declared data objects)
Compiler warning (Error) C5275	facade assembly 'name' being imported under '/clr'; missing option '/clr:netcore'?
Compiler warning (level 1, error) C5300	'#pragma omp atomic': left operand of 'operator' must match left hand side of assignment-expression
Compiler warning (level 1) C5301	'#pragma omp for': 'loop-index' increases while loop condition uses 'comparison'; non-terminating loop?
Compiler warning (level 1) C5302	'#pragma omp for': 'loop-index' decreases while loop condition uses 'comparison'; non-terminating loop?
Compiler warning (level 1) C5303	function marked with [[msvc::intrinsic]] did not result in a no-op cast
Compiler warning (level 1) C5304	a declaration designated by the using-declaration 'name1' exported from this module has internal linkage and using such a name outside the module is ill-formed; consider declaring 'name2' 'inline' to use it outside of this module
Compiler warning (level 1) C5305	'name': an explicit instantiation declaration that follows an explicit instantiation definition is ignored

See also

C/C++ Compiler and build tools errors and warnings
Compiler warnings C4000 - C5999