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Compiler Warning (level 4) C4001

Error Message

nonstandard extension 'single line comment' was used

Single-line comments are standard in C++ and nonstandard in C. Under strict ANSI compatibility (/Za), C files that contain single-line comments, generate C4001 due to the usage of a nonstandard extension. Since single-line comments are standard in C++, C files containing single-line comments do not produce C4001 when compiling with Microsoft extensions (/Ze).


To disable warning, uncomment #pragma warning(disable:4001).

// C4001.cpp
// compile with: /W4 /Za /TC
// #pragma warning(disable:4001)
int main()
   // single-line comment in main
   // C4001