Data directives and operators in inline assembly
Microsoft Specific
The inline assembler doesn't support all the data directives and operators available in MASM.
Remarks
Although an __asm block can reference C or C++ data types and objects, it can't define data objects with MASM directives or operators. Specifically, you can't use the definition directives DB, DW, DD, DQ, DT, and DF, or the operators DUP or THIS. MASM structures and records are also unavailable. The inline assembler doesn't accept the directives STRUC, RECORD, WIDTH, or MASK.
END Microsoft Specific