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Access to C and C++ compile-time constant expressions from embedded assembler

You can use the __cpp keyword to access C and C++ compile-time constant expressions, including the addresses of data or functions with external linkage, from the assembly code.

The expression inside the __cpp must be a constant expression suitable for use as a C++ static initialization. See 3.6.2 Initialization of non-local objects and 5.19 Constant expressions in ISO/IEC 14882:2003.

The following example shows a constant replacing the use of __cpp(expr):

LDR r0, =__cpp(&some_variable)
LDR r1, =__cpp(some_function)
BL  __cpp(some_function)
MOV r0, #__cpp(some_constant_expr)

Names in the __cpp expression are looked up in the C++ context of the __asm function. Any names in the result of a __cpp expression are mangled as required and automatically have IMPORT statements generated for them.