Porting C-Source to OS/400

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Qsicon Fixme.png 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.[1]

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.[2]

Preparations for QSYS.LIB

Preparations are mostly one on UNIX/Linux side.

  1. Convert Tabs to spaces:[3]
    for FILE in *.c *.h; do cp ${FILE} ${FILE}~; expand -i -t4 < ${FILE}~ > ${FILE}; done
  2. Find out longest line in all C- and H-Files.
    wc -L *.c |sort -rn |head
  3. 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. [4]
  4. 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),[5]
    2. One for H-Files (must be named H).
  5. 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[6][7].
    2. If the file names are longer, you'll have considerable fun to come up with shorter names, possibly grep through and replace in all text files if you needed to shorten a .h name, manually put together a textfile with approopriate put commands, and hope for the best.
  6. 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[8]

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)[9]

If compilation fails, output will go into a spooled file in QEZJOBLOG queue. This is the most tedious task. Compile, check output, fix problems, repeat.

Link object files to a program as follows: 

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

Footnotes

  1. ↑ It's possible to use stream files in IFS as compiler input, but compiled objects have to be put into a QSYS.LIB, library. So, the file name restrictions apply anyway. The line length problem is mostly gone, though.
  2. ↑ With V4R5, IBM claims to have implemented the C90 standard in Compiler and C-Library. I did not yet find a readymade config.h with all statements needed for a C90 environment.
  3. ↑ Tabs appear in SEU as only one blank. This makes source indentation hardly visible.
  4. ↑ Wider than 80 chars, that is.
  5. ↑ It could be clever to create one PF per subdirectory.
  6. ↑ Automatic login and switching to ASCII mode is done though a ~/.netrc-file.
  7. ↑ FTP ASCII takes care to convert ASCII to EBCDIC.
  8. ↑ This is a good example how to exploit the ftp server's ability to call CL commands as a replacement for rcmd.
  9. ↑ Possibly add SYSIFCOPT(*IFS64IO) if large file support is desired.
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