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When is an initializer element not a constant?
constchar.c:3:21: error: initializer element is not constant const char * str2 = str1; In fact, a “const char *” string is not a compile-time constant, so it can’t be an initializer. But a “const char * const” string is a compile-time constant, it should be able to be an initializer. I think this is a small drawback of CLang.
Can a static variable be initialized at compile time?
In such cases, the initialization cannot include execution of code, like calling a function or allocation a class. Initializer must be a constant whose value is known at compile time. You can then initialize your static variable inside of your init method (if you postpone its declaration to init).
Which is not a compile time constant in Clang?
In fact, a “const char *” string is not a compile-time constant, so it can’t be an initializer. But a “const char * const” string is a compile-time constant, it should be able to be an initializer. I think this is a small drawback of CLang. A function name is of course a compile-time constant.So this code works:
Do you have to initialize a macro before compile time?
Initializer must be a constant whose value is known at compile time. You can then initialize your static variable inside of your init method (if you postpone its declaration to init). You can certainly #define a macro as shown below. The compiler will replace “IMAGE_SEGMENT” with its value before compilation.
Is there a serial port library for wiringpi?
WiringPi includes a simplified serial port handling library. It can use the on-board serial port, or any USB serial device with no special distinctions between them. You just specify the device name in the initial open function. To use, you need to make sure your program includes the following file: Then the following functions are available:
When do brace-enclosed initializers need to be constants?
In C89/90 all brace-enclosed initializers were required to be constants. In C99 and later brace-enclosed initializers for objects with static storage duration must be constants. This is what you have in your case: sdp_header is an array with static storage duration, which means that you are only allowed to use constants between the {}.
What does errno do on a serial device?
This opens and initialises the serial device and sets the baud rate. It sets the port into “raw” mode (character at a time and no translations), and sets the read timeout to 10 seconds. The return value is the file descriptor or -1 for any error, in which case errno will be set as appropriate.