Error map
was not declared in this scope C++: error: 'x' was not declared in this scope (undeclared identifier)
C/C++ · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (10). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (10)
C/C++: undefined reference to `function' — collect2: error: ld returned 1 exit status
The linker can’t find the definition of a function or variable that was declared and used.
C/C++: error: expected ';' before 'x' — missing semicolon
The compiler reached a token where a statement should have ended — almost always a missing semicolon on the line above.
C++: error: expected primary-expression before ')' token
The parser expected a value or expression and found a token that cannot start one — often a type name passed where a value belong…
C++: error: 'string' does not name a type
Where the compiler expected a type, it found a name it does not know as one — a missing header, namespace, or class declared late…
C++: error: need 'typename' before 'T::iterator' because 'T' is a dependent scope
Inside a template, a name like `T::iterator` could be a type or a value, so C++ requires the `typename` keyword to say it is a ty…
C/C++: error: stray '\342' in program (smart quotes or invisible characters)
The source file contains a character the compiler does not recognise, typically curly quotes or a non-breaking space pasted from…
C++: error: expected unqualified-id before 'return' / before ')' token
The parser found a token where a name (declaration) was required — often a missing brace, a stray `)`, or a statement placed in a…
C++: error: 'optional' in namespace 'std' does not name a template type — wrong -std standard
The standard-library feature you used needs a newer C++ standard than the compiler is currently set to.
C: warning: implicit declaration of function 'foo' [-Wimplicit-function-declaration]
In C you called a function the compiler has not seen declared — usually a missing `#include`. Newer compilers treat it as an erro…
MSVC: error C2065: 'x': undeclared identifier
Visual C++ met a name it has not seen declared — a typo, a missing header or namespace, or use outside its scope.
Two steps away (21)
npm ERR! code ELIFECYCLE / Command failed with exit code 1
An npm script (build, start, test, postinstall) exited with an error. ELIFECYCLE is only the wrapper — the real error is printed…
gyp ERR! build error / node-gyp rebuild failed
A dependency with native C/C++ code couldn’t compile — missing build tools, Python, or an unsupported Node version.
COPY failed: file not found in build context / "/app/x": not found
The Dockerfile COPY refers to a path outside the build context, excluded by .dockerignore, or relative to the wrong directory.
Go: declared and not used: x / "fmt" imported and not used
Go refuses to compile code with unused local variables or unused imports.
Rust: error[E0308]: mismatched types — expected `X`, found `Y`
A value’s type doesn’t match what the context expects — common with &str vs String, Option/Result vs plain values, and integer ty…
C++: error: no matching function for call to 'f(int, const char*)'
No overload of the function accepts the arguments you passed — wrong count, wrong types, or a missing conversion.
C++: error: invalid conversion from 'const char*' to 'char*' [-fpermissive]
C++ forbids silently dropping `const` or converting between unrelated pointer types — typically a string literal assigned to `cha…
C++: error: invalid use of incomplete type 'class X' — forward declaration only
You used a class that has only been forward-declared (so its size and members are unknown) where the full definition is required.
C++: error: call of overloaded 'f(int)' is ambiguous
Two or more overloads fit equally well, so the compiler refuses to guess which function you meant.
C++: error: no match for 'operator<<' (operand types are 'std::ostream' and 'X')
You used an operator on a type that does not define it — most often printing your own class with `
C++: error: template argument deduction/substitution failed / couldn't deduce template parameter
The compiler could not work out the template arguments from your call — the arguments disagree, the type can't be deduced, or a c…
C++: error: cannot declare variable 'x' to be of abstract type 'Shape' (pure virtual functions)
You tried to create an object of a class that still has pure virtual functions; only a derived class that overrides all of them c…
C/C++: fatal error: foo.h: No such file or directory — #include not found
The preprocessor cannot find a header named in `#include`: wrong path, missing include directory (-I), or the library is not inst…
C++: error: redefinition of 'class X' / multiple definition — missing include guard
The same class, struct or function body was included twice in one translation unit because the header has no include guard.
Make: *** No rule to make target 'foo.c', needed by 'foo.o'. Stop.
`make` was asked to build a file for which there is no rule and no existing file — a missing source, a typo in the Makefile, or a…
C/C++: warning: control reaches end of non-void function [-Wreturn-type]
A function that promises a return value can finish without returning one on some path — undefined behaviour in C++.
C/C++: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' [-Wsign-compare]
A signed integer is compared with an unsigned one; the signed value is converted to unsigned, so a negative number becomes huge.
C: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=]
The `printf`/`scanf` format specifier does not match the argument's type, which is undefined behaviour and prints garbage or cras…
C/C++: ==ERROR: AddressSanitizer: heap-buffer-overflow on address — READ/WRITE of size N
AddressSanitizer caught a read or write just outside a heap block — an array index or length that is off by one or more.
C/C++: ==ERROR: AddressSanitizer: heap-use-after-free on address — memory used after delete/free
The program read or wrote a heap block after it had been freed; ASan shows who freed it and where it was allocated.
MSVC: error C4996: 'strcpy': This function or variable may be unsafe. Consider using strcpy_s instead
Visual C++ treats classic C library functions such as `strcpy`, `sprintf`, `fopen` and `scanf` as deprecated or unsafe and, with…
Map another error
Popular: 4035004000xC000007BTypeErrorCritical error404NullPointerException