Compiling program code files (.4gl)

Understanding .4gl source compilation

Genero BDL source code modules (with .4gl file extension) must be compiled to p-code modules (with .42m file extension) by using the fglcomp tool.

Compiled p-code modules are independent of the platform and processor architecture. They are interpreted by the Genero runtime system (fglrun).

The following lines show the compilation of the prog.4gl source, in a UNIX™ shell session:

$ cat prog.4gl
MAIN
  DISPLAY "hello"
END MAIN

$ fglcomp prog.4gl

$ ls -s prog.42m
   4 prog.42m

Automatic compilation of imported modules

When compiling a .4gl module that imports other modules with the IMPORT FGL instruction, fglcomp will automatically compile the imported modules, if they are located in the same directory of the current module, and if the .4gl source is more recent as the .42m file.

For more details, see Importing modules.

Handling fglcomp compiler errors

If an error occurs, the compiler writes by default an error file with the .err extension.

$ cat prog.4gl
MAIN
  LET x = "hello"
END MAIN

$ fglcomp prog.4gl
Compilation was not successful. Errors found: 1.
 The file prog.4gl has been written.

$ cat prog.err
MAIN
  LET x = "hello"
| The symbol 'x' does not represent a defined variable.
| See error number -4369. 
END MAIN

With the -M option, you can force the compiler to display an error message instead of generating an .err error file:

$ fglcomp prog.4gl
xx.4gl:2:8 error:(-4369) The symbol 'x' does not represent a defined variable.

Produce compiler warnings with -W

By default, the compiler does not raise any warnings.

To improve code quality, enable compiler warnings with the -W option:

$ cat prog.4gl
MAIN
  DATABASE test1
  SELECT COUNT(*) FROM x, OUTER(y) WHERE x.k = y.k
END MAIN

$ fglcomp -W stdsql prog.4gl
xx.4gl:3: warning: SQL statement or language instruction with specific SQL syntax.

When a warning is raised, you can use the -W error option to force the compiler to stop as if an error was found.

For more details about the -W option, see Arguments for the -W option.

Verbose compilation

$ fglcomp --verbose main.4gl
[parsing main.4gl]
[compiling: fglcomp --import-by=main --verbose  mod1]
[parsing mod1.4gl]
[compiling: fglcomp --import-by=main,mod1 --verbose  mod2]
[parsing mod2.4gl]
[writing mod2.42m]
[loading mod2.42m]
[writing mod1.42m]
[loading mod1.42m]
[writing main.42m]