PBMAIN — Program Entry Point

Description

PBMAIN is the designated entry point for PBXA64 executable programs (compiled with #COMPILE EXE). When the operating system launches the program, execution begins at PBMAIN. This is analogous to main() in C or WinMain in traditional Windows programming.

PBMAIN must be declared as a FUNCTION returning LONG and takes no parameters. The return value is the program's exit code, where 0 typically indicates success and non-zero values indicate error conditions. This exit code is available to the calling process or shell.

Every PBXA64 executable must have exactly one PBMAIN function. DLL projects (#COMPILE DLL) do not use PBMAIN and instead rely on DllMain for initialization.

Parameters

Example

#COMPILE EXE

FUNCTION PBMAIN() AS LONG
    LOCAL cmdLine AS STRING

    PRINT "PBXA64 Program Started"
    cmdLine = COMMAND$

    IF LEN(cmdLine) > 0 THEN
        PRINT "Arguments: "; cmdLine
    ELSE
        PRINT "No arguments provided."
    END IF

    PRINT "Program finished."
    FUNCTION = 0    ' Exit code 0 = success
END FUNCTION

Generated Assembly

CRT Startup & Entry Point

; The linker sets the PE entry point to __pb_crt_startup
__pb_crt_startup:
    sub    rsp, 288h                   ; Shadow space for WinAPI calls
    xor    ecx, ecx                    ; dwFlags = 0 (console app)
    call   [__imp_SetConsoleMode]      ; Initialize console I/O
    add    rsp, 288h

    xor    ecx, ecx                    ; Clear RAX for return value
    call   PBMAIN                      ; Jump to user code

    mov    ecx, eax                    ; Exit code = PBMAIN return value
    call   [__imp_ExitProcess]         ; Terminate process
    ret

PBMAIN Prologue

PBMAIN:
    push   rbp
    mov    rbp, rsp
    sub    rsp, frame_size             ; Allocate stack frame for LOCALs
    ; ... body ...
    mov    rax, [rbp - return_offset]  ; Load FUNCTION = value
    add    rsp, frame_size
    pop    rbp
    ret

Notes

• PBMAIN is only valid when #COMPILE EXE is specified. It must not appear in DLL projects.
• The return type must always be AS LONG. Returning other types will produce a compile-time error.
• If PBMAIN is missing from an EXE project, the compiler reports an error at link time.
• Use COMMAND$ to retrieve the full command line passed to the program. Use COMMAND$(n) to access individual arguments by index.
• PBXA64 initializes the runtime library automatically before PBMAIN is called. No manual initialization is required.
• Console windows are automatically allocated for console-mode EXEs. For GUI applications, use the appropriate subsystem option.