Porting C-Source to OS/400

This article isn't finished yet or needs to be revised. Please keep in mind that thus it may be incomplete. Reason: Complete with Links to all necessary Books.

Because of the uncommon file handling, name length and character constraints, porting is already a mostly manual task.

Most often, the real challenge is to manually put together a config.h file. Since there's no capable UNIX shell environment, ./configure is no option.

These are definitions for integers, being used often.

typedef unsigned long long int uint64_t;
typedef unsigned int uint32_t;
typedef unsigned short int uint16_t;

Note: The IMPI (CISC) C compiler in V3R2 and earlier doesn't know long long, it's 32 bits only.

Preparations for QSYS.LIB

Preparations are mostly one on UNIX/Linux side. This is required to make the older V4R5 compiler happy. Newer compilers might be more forgiving.

1. Convert to native line endings for your platform, if the source files don't match.
2. Convert Tabs to spaces:
   for FILE in *.c *.h; do cp ${FILE} ${FILE}~; expand -i -t4 < ${FILE}~ > ${FILE}; done
3. Find out longest line in all C- and H-Files.
   wc -L *.c |sort -rn |head
4. Eliminate too long lines by wrapping. This is easily done with set colorcolumn=80 in vim, and scrolling through the files with a wide window.
5. Find C++-style comments and convert to proper C comments.
6. Find function definitions which should be inlined, remove the word "inline" from the definition, and add a hint for the preprocessor/compiler that a function should be inlined before the function definition: #pragma inline (functionname)
7. Find and remove text following #endif preprocessor statements in the same line (thought as comment).
8. Create (at least) two appropriate SRCPF with matching maximum line lengths through the RCDLEN parameter for CRTSRCPF:
   1. One (or more) for C-Files (may be named QCSRC),
   2. One for H-Files (must be named H).
9. Upload.
   1. If the file names are already shorter than 10 Characters (excluding file extension), just upload to a SRC PF:
      for FILE in *.c; do echo -n "put ${FILE} MYLIB/QCSRC."; basename ${FILE} .c; done |ftp as400.
   2. If the file names are longer, you'll have considerable fun to come up with shorter names. Possibly grep through, and replace names in all text files if you needed to shorten a .h name. Finally, put together a text file with appropriate put commands, and hope for the best.
10. Change file type to C:
    for FILE in *.c; do echo "quote rcmd CHGPFM FILE(MYLIB/QCSRC) MBR($(basename ${FILE} .c)) SRCTYPE(C)"; done |ftp as400 Note: You'll need to do this for header files, also!

The precompiler searches private includes in *LIBL/H, without the .h-Extension.

Compile Cycle

Compile object files as follows:

CRTCMOD MODULE(MYLIB/MAIN) SRCFILE(MYLIB/QCSRC) DEFINE(DEF1 DEF2=1) OPTION(*LOGMSG) OUTPUT(*PRINT)

• Add SYSIFCOPT(*IFSIO *IFS64IO) to the compiler parameters if the code contains fopen() calls.
• If you added #pragma inline (functionname) to the code, add INLINE(*ON) to the compiler parameters

If compilation fails, output will go into a spooled file in the configured output queue. This is the most tedious task.

1. Compile,
2. check output,
3. fix problems,
4. goto 1.

If all object modules have been created, you can then link them to a *PGM object as follows:

CRTPGM PGM(MYLIB/MYPG) MODULE(MYLIB/*ALL) ENTMOD(*PGM) ACTGRP(*NEW) DETAIL(*BASIC)