Error map
implicit declaration of function C: warning: implicit declaration of function 'foo' [-Wimplicit-function-declaration]
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++: error: 'x' was not declared in this scope (undeclared identifier)
The compiler met a name it has never seen: it is misspelled, declared later, out of scope, or its header or namespace is missing.
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.
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/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++: multiple definition of `x'; first defined here — ld returned 1 exit status
The linker found the same function or global variable defined in two object files — usually something defined in a header.
C/C++: Segmentation fault (core dumped) — SIGSEGV from a null, dangling or out-of-bounds pointer
The program touched memory it is not allowed to access — a null or dangling pointer, an out-of-range array index, or a stack over…
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…
Two steps away (25)
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.
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/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: '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.
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++: error: use of deleted function 'X::X(const X&)' — copying a non-copyable type
The code needs a function (usually a copy constructor or assignment) that was deleted explicitly or implicitly, as for `std::uniq…
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++: error: 'int X::secret' is private within this context
Code outside the class tried to use a private (or protected) member.
C/C++: runtime error: signed integer overflow / null pointer / shift exponent too large (UndefinedBehaviorSanitizer)
UBSan detected code that triggers undefined behaviour (overflow, null dereference, out-of-bounds index, bad shift, misaligned acc…
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: 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: narrowing conversion of 'x' from 'int' to 'char' inside { } [-Wnarrowing]
Brace initialisation `{}` refuses conversions that can lose data, such as `double` to `int` or a runtime `int` to `char`.
C/C++: *** stack smashing detected ***: terminated — buffer overflow on the stack
GCC's stack protector noticed that a local buffer overflowed and overwrote the function's canary value, so it aborted the program.
C++: undefined reference to `vtable for X' — virtual function not defined
The linker cannot find the class's virtual table, which means at least one virtual member function was declared but never defined…
C/C++: undefined reference to `main' — (.text+0x20) in crt1.o
The linker has no `main` function: the file with `main` is not compiled or linked, or `main` is spelled or declared incorrectly.
C/C++: undefined reference to `pthread_create' — missing -pthread (also `dlopen`, `clock_gettime`)
Your program uses threads (or another system library) but the linker was not told to link it.
Segmentation fault (core dumped)
A program accessed memory it wasn’t allowed to, and the kernel killed it with SIGSEGV (exit code 139).
C/C++: free(): double free detected / double free or corruption (out) — Aborted (core dumped)
Memory was freed twice or the heap was corrupted (buffer overflow, freeing a non-heap pointer), so glibc aborted the program.
C/C++: Assertion `x > 0' failed. Aborted (core dumped) — assert() condition was false
An `assert()` in your code or in a library found its condition false and aborted the program on purpose.
MSVC: fatal error LNK1104: cannot open file 'foo.lib' (or 'app.exe' while it is running)
The Visual C++ linker could not open an input library or the output file — the path is wrong, the library is missing, or the .exe…
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.
Map another error
Popular: 4035004000xC000007BTypeErrorCritical error404NullPointerException