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Conventions and Feedback Overview of the Compiler Getting Started with the Compiler Compiler Features Compiler Coding Practices Compiler Diagnostic Messages Using the Inline and Embedded Assemblers of the AR Compiler support for inline assembly language Inline assembler support in the compiler Restrictions on inline assembler support in the co Inline assembly language syntax with the __asm key Inline assembly language syntax with the asm keywo Inline assembler rules for compiler keywords __asm Restrictions on inline assembly operations in C an Inline assembler register restrictions in C and C+ Inline assembler processor mode restrictions in C Inline assembler Thumb instruction set restriction Inline assembler Vector Floating-Point (VFP) restr Inline assembler instruction restrictions in C and Miscellaneous inline assembler restrictions in C a Inline assembler and register access in C and C++ Inline assembler and the # constant expression spe Inline assembler and instruction expansion in C an Expansion of inline assembler instructions that us Expansion of inline assembler load and store instr Inline assembler effect on processor condition fla Inline assembler operands in C and C++ code Inline assembler expression operands in C and C++ Inline assembler register list operands in C and C Inline assembler intermediate operands in C and C+ Inline assembler function calls and branches in C Behavior of BL and SVC without optional lists in C Inline assembler BL and SVC input parameter list i Inline assembler BL and SVC output value list in C Inline assembler BL and SVC corrupted register lis Inline assembler branches and labels in C and C++ Inline assembler and virtual registers Embedded assembler support in the compiler Embedded assembler syntax in C and C++ Effect of compiler ARM and Thumb states on embedde Restrictions on embedded assembly language functio Compiler generation of embedded assembly language Access to C and C++ compile-time constant expressi Differences between expressions in embedded assemb Manual overload resolution in embedded assembler __offsetof_base keyword for related base classes i Compiler-supported keywords for calling class memb __mcall_is_virtual(D, f) __mcall_is_in_vbase(D, f) __mcall_offsetof_vbase(D, f) __mcall_this_offset(D, f) __vcall_offsetof_vfunc(D, f) Calling nonstatic member functions in embedded ass Calling a nonvirtual member function Calling a virtual member function Legacy inline assembler that accesses sp, lr, or p Accessing sp (r13), lr (r14), and pc (r15) in lega Differences in compiler support of inline and embe

__offsetof_base keyword for related base classes in embedded assembler

ARM Compiler toolchain v5.02 for µVision Using the Compiler
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__offsetof_base keyword for related base classes in embedded assembler

The __offsetof_base keyword enables you to determine the offset from the beginning of an object to a base class sub-object within it:

__offsetof_base(D, B)

B must be an unambiguous, nonvirtual base class of D.

Returns the offset from the beginning of a D object to the start of the B base subobject within it. The result might be zero. Example 24 shows the offset (in bytes) that must be added to a D* p to implement the equivalent of static_cast<B*>(p).

Example 24. static_cast<B*>(p)

__asm B* my_static_base_cast(D* /*p*/) // equivalent to:
                                       // return static_cast<B*>(p)
{
    if __offsetof_base(D, B) <> 0 // optimize zero offset case
        ADD r0, r0, #__offsetof_base(D, B)
    endif
    BX lr
}

The __offsetof_base, __mcall_*, and _vcall_offsetof_vfunc keywords are converted into integer or logical constants in the assembler source. You can only use it in __asm functions, not in __cpp expressions.

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