Compiler Option: -entry

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=CompilerOptentry
• Last revised: 2021-10-12

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Override the public exported name of the implicit user main function

Syntax

-entry< name >`

`

Parameters

name

The custom name that overrides the public exported name of the implicit user main function

Description

The -entry compiler option changes the name of the publicly export symbol of the implicit user main function (automatically generated by fbc as start-up code).

It affects the start-up code and implicit user main, which is also affected by the module being the main module or not.

By default, fbc defines a publicly exported 'main' symbol in the main module as required by the run time start-up system code.

There is no other way currently to override fbc's use of the 'main' symbol other than to always compile and link separately.

Proceedings:

• The custom main function name must only be declared with the following signature (same parameter types, same return type, same calling convention) to be compatible with the (basic) main function:

start GeSHi

'' internally the implicit main function is now named "custom_main"
Declare Function custom_main CDecl Alias "custom_main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long

end GeSHi

• The (basic) main function must also be provided to satisfy the linker and start-up code. This might be defined in another libray or framework, in C, or ASM, or fb language as shown by the following minimum code example:

start GeSHi

Function main CDecl Alias "main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long
    '' .....
    '' call the custom main
    Return custom_main( argc, argv )
End Function

end GeSHi

• Then compile with the -entry custom_main option.

Note:

This feature is being developed and may change in future (see Compiler Option: -entry in Documentation forum).

There will maybe a better way to deal with this: a compiler option that lets to outright specify an explicit "main".

Examples

Example of program (option_entry.bas) trying to show the minimal code for fb language only:

start GeSHi

'' option_entry.bas:

'' - demonstrate alternate named main function
''   as an alternate entry point for the implicit user main
'' - we also can compile and link in separate steps

'' compile: $ fbc -c -m option_entry option_entry.bas -entry custom_main
'' compile: $ fbc option_entry.o
'' OR
'' compile: $ fbc option_entry.bas -entry custom_main

'' internally the implicit main function is now named "custom_main"
Declare Function custom_main CDecl Alias "custom_main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long

'' But we still need a main() function to satisfy the linker and start-up code
'' - this might be defined in another libray or framework
'' - it's not so let's define it here for the demonstration
Function main CDecl Alias "main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long
    '' just call our custom main for demonstration
    Return custom_main( argc, argv )
End Function

'' ---------------------------------
'' START OF USER'S IMPLICIT MAIN
'' internally this is named "custom_main" and will automatically be
'' called by our custom frame work

Print "hello"
Sleep

'' END OF USER'S IMPLICIT MAIN
'' ---------------------------------

end GeSHi

Version

• Since fbc 1.09.0

See also

• Compiler Option: -m
• Executables

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