NASM-X

2.7: ENDIF

Description

Terminates an IF block.

Syntax

ENDIF

Examples

2.8: ENDPROC

Description

Terminates a PROC block.

Syntax

ENDPROC

Examples

2.9: ENDLOCALS

Description

Terminates a LOCALS block.

Syntax

ENDLOCALS

Examples

2.10: ENDWHILE

Description

Terminates a WHILE block.

Syntax

ENDWHILE

Examples

2.11: IF

Description

This macro causes conditional branching of the program execution.

Syntax

     IF reg,cc,val

     where:
         reg is the register used for comparison
         cc is the condition to check
         val is the value to compare the register against

Example

Section E.2

2.12: IMPORT: Importing Symbols from Other Modules

Description

This macro causes the external procedure name provided to be made available to your program to call.

Syntax

     IMPORT [callconv,] proc_name [,param[,param,...]]

     where:
          callconv is the calling convention used if not the default.
               supported conventions: CDECL, FASTCALL, NAKED, PASCAL, STDCALL
          proc_name is the name of the procedure to import.
          param is the type and parameter name(s) of the procedure.

Example

2.13: INVOKE

Description

This macro causes procedure name to be called.

Syntax

     INVOKE [callconv,] proc_name [,param[,param,...]]

     where:
          callconv is the calling convention used if not the default.
               supported conventions: CDECL, FASTCALL, NAKED, PASCAL, STDCALL
          proc_name is the name of the procedure to call.
          param is the parameter type and value of the called procedure.

Notes

Fox Windows x64 programming:
INVOKE will not normally spill register arguments to the stack prior to the call. If this behavior is desired due to calling a non-conformant function then you may use NASMX_PRAGMA INVOKE_FASTCALL_STACK_PRELOAD, ENABLE prior to INVOKE to enable this behavior and then disable the pragma after INVOKE.

Example

2.14: LOCAL

Description

This macro creates variable space for the procedure on the stack.

Syntax

     LOCAL varname, type, qty

     where:
          varname is the name of the local variable.
          type is the type of the local variable being created.
          qty is the number of types needed ( default: 1 ).

Example

2.15: LOCALS

Description

This macro marks the beginning of procedure local variables. It must be the next immediate macro after PROC.

Syntax

     LOCALS [NONE]

     where:
          NONE is an optional value indicating the procedure does not use local stack variables.
          Note that the macro ENDLOCALS is not required when LOCALS NONE is specified.

Example

2.16: NASMX_AT: Structure instance assignment

Description

This macro allocates structure member space.

Syntax

     NASMX_AT name, value

     where:
          name provides the name of the structure member offset.
          value specifies the data value to be initially assigned.

Example

2.17: NASMX_ENDSTRUC: Ending a structure definition

Description

This macro is used to indicate that the structure currently being defined is now completed.

Syntax

NASMX_ENDSTRUC

Example

2.18: NASMX_ENDUNION: Ending a union definition

Description

This macro is used to indicate that the union currently being defined is now completed.

Syntax

NASMX_ENDUNION

Example

2.19: NASMX_IENDSTRUC: Ending a structure instance

Description

This macro is used to indicate that the structure currently being allocated is now completed.

Syntax

NASMX_IENDSTRUC

Example

2.20: NASMX_ISTRUC: Beginning a structure instance

Description

This macro is used to create a structure instance.

Syntax

     NASMX_ISTRUC name, type

     where:
          name is the name of this structure instance.
          type is the name of the predefined structure type.

Example

2.21: NASMX_PRAGMA: Defining pragmas

Description

This macro allows the developer to specify certain options that affect how NASMX generates code.

Syntax

     NASMX_PRAGMA directive,option [,options]

     where:
          directive provides instruction to NASMX
          options are optional values specified for the directive.
     directives:
          CALLSTACK, size ; Win64 minimum callstack size is 32
          PACK, PUSH, align_val ; default is natural structure member alignment
          PACK, POP
          PROC_FASTCALL_STACK_PRELOAD, [ ENABLE | DISABLE ] ; default is enable
          INVOKE_FASTCALL_STACK_PRELOAD, [ ENABLE | DISABLE ] ; default is disable

Note: The pragma INVOKE_FASTCALL_STACK_PRELOAD is applicable only for Windows 64-bit.

Example

Please see demos

2.22: NASMX_RESERVE: Defining structure/union members

Description

This macro allows the developer to specify the structure member variable names and types.

Syntax

     NASMX_RESERVE name, type, qty

     where:
          name provides the name of the structure member.
          type specifies the data type of the member.
          qty specifies how many types to reserve ( Default: 1 ).

Example

2.23: NASMX_STRUC: Defining Structures

Description

This macro allows the developer to begin structure definition and provide a name.

Syntax

     NASMX_STRUC name

     where:
          name provides the name of the structure.

Example

2.24: NASMX_TCHAR: Character portability

Description

This macro is used to indicate that the character type for the defined label will change based on the UNICODE define.

Syntax

NASMX_TCHAR

Example

2.25: NASMX_TEXT: Character portability

Description

This macro is used to indicate that the character type for the defined label will change based on the UNICODE define.

Syntax

NASMX_TEXT

Example

2.26: NASMX_UNION: Defining a union

Description

This macro allows the developer to begin a union definition and provide a name.

Syntax

     NASMX_UNION name

     where:
          name provides the name of the union.

Example

2.27: PROC

Description

This macro causes the named procedure to be defined.

Syntax

     PROC [callconv,] proc_name [,param[,param,...]]

     where:
          callconv is the calling convention used if not the default.
               supported conventions: CDECL, FASTCALL, NAKED, PASCAL, STDCALL
          proc_name is the name of the procedure.
          param is the type and parameter name(s) of the procedure.

Notes

The stack frame is automatically created whenever you have defined either procedure parameters or local stack variables. Arguments are always located on the stack above the return address for both 32-bit and 64-bit. The 32-bit register EBP ( RBP in 64-bit ) is used as the frame pointer. Procedures that define parameter arguments will have the parameter names equated to offsets from the frame. Use the macro argv() to access the procedure arguments.

For the 64-bit fastcall calling convention:
By default, during the procedure prologue, NASM-X will automatically save the registers used for the procedure parameters you define to the stack. To prevent NASM-X from saving register parameters to the stack you can place a NASMX_PRAGMA PROC_FASTCALL_STACK_PRELOAD, DISABLE at the beginning of your source file after including nasmx.inc
You may enable or disable stack pre-loading at any time by using multiple NASMX_PRAGMA directives in your source file.

For Linux 64-bit mode:
NASM-X will create a register argument spill area below the return address in a manner similar to local variables. Automatic register argument saving is enabled or disabled as indicated previously. The macro argv() will correctly provide the parameter offsets in this area.

Finally, if your procedure does not require automatic register saves or you will not access the register spill area then you may simply define a PROC without parameters. Doing so may eliminate the need to use register EBP/RBP to create the stack frame depending on whether local variable stack space is required or not thus freeing up that register for use. The exceptions are 1.) the program main entry point which, if defined, must establish the initial frame; and 2.) procedures that expect floating point arguments must be prototyped in order for INVOKE to assign the appropriate floating point registers.

Known Issues

There is currently no support for passing parameter values larger than 64-bits.
For Linux 64-bit mode NASM-X currently does not support defining a PROC with more parameters than the maximum registers defined for the x64 fastcall calling convention. The INVOKE macro, however, fully supports the calling convention.

Example

2.28: PROTO: Exporting Symbols to Other Modules

This macro generates a global procedure name that can be imported by additional source modules.

Syntax

     PROTO [callconv,] proc_name [,param[,param,...]]

     where:
          callconv is the calling convention used if not the default.
               supported conventions: CDECL, FASTCALL, NAKED, PASCAL, STDCALL
          proc_name is the name of the procedure.
          param is the type and parameter name(s) of the procedure.

2.29: REPEAT: starting a loop

Description

This macro creates a procedure specific label to implement a looping block.

Syntax

REPEAT

Examples

2.30: RETURN: returning from a procedure

Description

This macro causes a jump to the procedure epilogue.

Syntax

     RETURN [ val ]

     where val is the optional procedure return value

Examples

See demos/win32/demo2 for example usage.

Notes

At the end of your procedure you may simply mov eax, val as the last statement to be executed in order to optimize out the jump to the procedure epilogue.

2.31: UNTIL: loop condition

Description

Specifying a REPEAT block terminating condition.

Syntax

     UNTIL reg,cc,val

     where:
         reg is the register used for comparison
         cc is the condition to check
         val is the value to compare the register against

Examples

2.32: USES: Saving registers to the stack

Description

This macro enables the developer to specific registers that must be saved during the procedure prologue. Saved registers are restored automatically by NASMX during ENDPROC.
This macro, if used, must appear immediately following a PROC statement and immediate before the LOCALS statement

Syntax

USES reg [,reg [,reg...]]

Examples

2.33: WHILE: looping

Description

This macro creates a procedure specific label to implement a looping block.

Syntax

     WHILE reg,cc,val

     where:
         reg is the register used for comparison
         cc is the condition to check
         val is the value to compare the register against

Examples