Slide 14.2: High-level language interface Slide 14.4: Inline assembly code (cont.) Home

Inline Assembly Code (Cont.)

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Features
Here is what you can do when writing inline assembly code:

• Use any instruction from the Intel instruction set.
• Use register names as operands.
• Reference function parameters by name.
• Reference code labels and variables declared outside the asm block.
• Use numeric literals that incorporate either assembler-style or C-style radix notation such as 0A2Ch and 0xA2C.
• Use the PTR operator in statements such as inc BYTE PTR[esi].
• Use the EVEN and ALIGN directives.

Limitations
You can not do the following when writing inline assembly code:

• Use data definition directive such as DB (BYTE) and DW (WORD).
• Use assembler operators (other than PTR).
• Use STRUCT, RECORD, WIDTH, and MASK.
• Use macro directive, including MACRO, REPT, IRC, IRP, and ENDM, or macro operators (<>, !, &, %, and .TYPE).
• Reference segments by name.

Length, Type, and Size
You can use the LENGTH, SIZE, and TYPE operators with the inline assembler. The LENGTH operator returns the number of elements in an array. The TYPE operator returns one of the following, depending on its target:

• The number of bytes used by a C/C++ type or scalar variable
• The number of bytes used by a structure
• For an array, the size of a single array element

The SIZE operator returns LENGTH×TYPE. Microsoft Visual C++ inline assembler does not support the SIZEOF and LENGTHOF operators.