If there is such an output statement in C code, would the output be "Continue???(y/n)"? For example: `printf("Continue???(y/n)\n");`. In fact, the result of the above statement is "Continue?[y/n)\n". A colleague sent a company-wide email for help to ask about the reason for this output.
The reason for this phenomenon is related to the way the C compiler processes string literals. Specifically, in some compilers (such as Microsoft Visual C++), the question mark (`?`) has a special meaning when it appears in combination with other characters in a string literal. This is due to support for trigraphs or escape sequences in certain environments.
In this case:
- The sequence `??(` in the string is interpreted as a trigraph that represents the `[` character.
- Similarly, `??)` represents the `]` character.
Thus, the string `"Continue???(y/n)\n"` is interpreted by the compiler as `"Continue?[y/n]\n"`, which explains the unexpected output.
To avoid this issue, you can disable trigraph processing in the compiler settings or ensure that the source file does not inadvertently use trigraph sequences. Alternatively, you can rewrite the string to explicitly use the desired characters, such as `"Continue?(y/n)\n"`, avoiding trigraph sequences entirely.