42m module information

Describes how to handle module information in .42m p-code files.

Compiler and runtime compatibility

The runtime system (fglrun) used to execute programs must be compatible with the fglcomp compiler version used to build the .42m modules.

To control this compatibility, the compiler writes Genero and p-code version information in the generated 42m files, in the p-code header.

The compiler also writes additional information in the p-code header, such as the source filename used at compilation, a timestamp, or a user-defined string/tag.

The p-code header information of a 42m file can be read with the fglrun -b module.42m command. This is useful on production sites, to check the version of the compiler that was used to build the 42m nodules.

It is also possible to get additional information about the p-code module such as the size used in memory with fglrun --module-size.

Identifying the version of the compiler and runtime system

To check if the version of the compiler or runtime system, use the -V option:
$ fglcomp -V
fglcomp 4.00.03 internal-build-number
Genero 4gl compiler
Target l64xl217

$ fglrun -V
fglrun 4.00.03 internal-build-number
Genero virtual machine
Target l64xl217

Extracting p-code header information

To extract build information from a .42m file, run fglrun with the -b option:

$ fglrun -b mymodule.42m
3.10.12 /home/devel/stores/mymodule.4gl 24

The p-code header contains the following fields:

  1. An optional timestamp, if the --timestamp option was used with fglcomp.
  2. The Genero product version.
  3. The full path of the source file, or the module name, if the --omit-source-name option was used with fglcomp.
  4. The internal identifier of the p-code version.
  5. An optional user-defined tag, if the --tag=string option was used with fglcomp.

Avoiding the full source file path in the p-code header

By default, fglcomp writes the source filename (full path) in the resulting .42m module:
$ fglcomp mymodule.4gl

$ fglrun -b mymodule.42m
3.10.12 /home/devel/stores/mymodule.4gl 24

To avoid the source name in the .42m module, use the --omit-source-name option of fglcomp, to write only the module name in the p-code header:

$ fglcomp --omit-source-name mymodule.4gl

$ fglrun -b mymodule.42m
3.10.12 mymodule 24

Writing a custom string to the p-code header

Use the --tag="custom-string" option of fglcomp, to add a user-defined string to the p-code header. When reading p-code header information with fglrun -b, the user-defined string is printed as tag="custom-string".

The tag field can for example be used to stamp the 42m file with the custom product version:
$ fglcomp --tag="OXOGEN 5.23" mymodule.4gl

$ fglrun -b mymodule.42m
3.10.12 /home/devel/stores/mymodule.4gl 24 tag="OXOGEN 5.23"

Writing a compilation timestamp to the p-code header

To write timestamp information in the p-code header, use the --timestamp option of fglcomp:

$ fglcomp --timestamp mymodule.4gl

$ fglrun -b mymodule.42m
2008-12-24 11:22:33 3.10.12 /home/devel/stores/mymodule.4gl 24

When using the --timestamp compiler option to write build timestamp information in p-code modules, you will not be able to easily compare 42m files (based on a checksum, for example). Without the timestamp, fglcomp generates exactly the same p-code module as if the source file was not modified.

Reading p-code header of older versions

fglrun -b can read the header of p-code modules compiled with older versions of fglcomp and display version information for such old modules.

If fglrun cannot recognize a p-code module, it returns an execution status that is different from zero.

Reading p-code header of 42x and 42r files

When reading build information of a 42x or 42r file, fglrun scans all modules used to build the library or program. You will see different versions in the first column if the modules were compiled with different versions of fglcomp. However, it's not recommended that you mix versions on a production site:

$ fglrun -b myprogram.42r
3.10.11 /home/devel/stores/mymodule1.4gl 24
3.10.02 /home/devel/stores/mymodule2.4gl 24
3.10.12 /home/devel/stores/mymodule3.4gl 24

Computing the p-code size of a module or program

The fglrun command provides the --module-size option to compute the p-code size of a module:

$ fglrun --module-size mymodule.42m
 12.34K mymodule
This size is defined by the amount of p-code instructions of the module.

P-code modules are shared by all fglrun instances executing on the same computer. For more details, see Elements shared by multiple programs.

The --program-size option reports the total p-code size of all modules of a program. The argument must be a .42m module containing the MAIN (with main module importing other modules by IMPORT FGL):
$ fglrun --module-size myprogram.42m
  0.34K module1
  2.59K module2
12.76K total

The --program-size option can also use a .42r program file as argument, for linked programs:

$ fglrun --module-size myprogram.42r
  0.34K module1
  2.59K module2
12.76K total