Developing Software on Linux

1. Developing Software on Linux Tim Marriott Mel Nicholson ICCAD 2003

2. Introduction • Why Linux? • Porting to Linux • Developing on Linux

3. Why Linux? • The question should be “Why the PC?” • Inexpensive Performance • What is wrong with Windows as the OS? • It is too different from Unix • Major EDA software runs on Unix • The initial port is tough and the continued support is difficult • Linux is a robust OS that is very close to Unix • The initial port is easy and the continued support is also easy • It is in the right place at the right time

4. Why Linux? • We port to Linux because customers want it • Fast Hardware • Inexpensive Hardware • It’s an easy port • We develop on Linux because it increases our productivity • Fast Hardware • Inexpensive Hardware • Not a steep learning curve for our developers

5. Porting to Linux • Porting Overview • What Linux to choose? • Problems with the Linux Support Story • The Enterprise is Coming • Porting Issues Encountered

6. Porting Overview • Linux is really just another flavor of Unix • The port was not difficult • The issues encountered were no more difficult than between flavors of Unix • Very few problems were encountered • OS and hardware configuration took the most time to get right

7. What Linux to Choose? • Versioned Linux was the gating factor to delivering a port • Can’t base a product on all variants of the OS that the open source community produces • Various companies supply versioned variants of Linux • Red Hat, SuSE, Caldera, Mandrake • Synopsys chose Red Hat

8. Problems with the Linux Support Story • Linux companies didn’t deliver a true enterprise support structure • Versions are not compatible • No long term support of versions • No compatibility guarantees between patches • Versions release very often • ISV’s stay with old versions for long periods of time • Synopsys is still based on Red Hat 7.2 • Linux companies have recognized the flaw • Enterprise versions are becoming available • Consumer versions are unfriendly to business

9. The Enterprise is Coming • Red Hat now only supports an Enterprise version • Yearly subscription based support • Guaranteed binary and API compatibility between versions • 12-18 months between major releases • Cost will increase • Stability will offset the additional cost • Red Hat Enterprise Linux WS $179 - $299 on x86 • $792 on Itanium and AMD64 Information on this slide from http://www.redhat.com

10. Porting Issues Encountered • Calling fclose() on a file that is not open crashes • Be sure to only call fclose() once per open file • Binary files are not platform independent due to Little Endian byte order • Must decide where you want to handle the conversion when reading/writing binary files

11. Porting Issues Encountered • Gcc doesn’t increment i++ until the end of the statement • result = foo(x[i++], x[i]); • Increment some other way • i and i+1 is one option • C compiler has problems with nested function calls and function calls in “if” statements • Use separate statements instead

12. Porting Issues Encountered • “/bin” and “/usr/bin” are separate directories • Make sure command location is defined for Linux • Default sorting order is not the same • Set environment variable LC_ALL to C

13. Porting Issues Encountered • Can’t initialize global scope to be stdout or stdin • stdout/stdin are not constant expressions and are therefore not suitable for initialization • If a NULL pointer is passed to fclose it will crash • Check the pointer • if (fd) fclose(fd);

14. Porting Issues Encountered • intptr_t is not defined in int_types.h • It is defined in stdint.h • SIGEMT is not defined • Do not use SIGEMT

15. Porting Issues Encountered • The default floating point precision varies • Uses native support of underlying hardware • Different results for register operation versus loaded • Makes golden-file based regression testing difficult • IEEE compliance options incur a performance penalty

16. Developing on Linux • Linux Development Model • Office Productivity Tools • Developer Tools • GUI Development

17. Linux Development Model SCM Data Servers Linux Box 2 CPU 4 GB Memory Exceed Vnc Big Local Disk Windows Desktop Computer Room

18. Office Productivity Tools • Windows Desktop avoids the office productivity tool issues • OpenOffice and StarOffice available on Linux • MS Office compatible • CodeWeavers CrossOver Office • Allows MS Office to run directly on Linux • VMware dual operating system capable

19. Developer Tools • Compilers • Gnu (gcc, g++) • Intel Compilers • Debuggers • gdb • Graphical front end, ddd

20. Developer Tools • Editors (IDE’s) • Emacs, Vim • Highly configurable editors • Can tightly integrate gdb and SCM systems • Kdevelop • Full integrated MS Visual C++ style IDE • Source Control Systems • Clearcase, Perforce, CVS, RCS

21. Developer Tools • Memory Debug • Purify (Available Soon) • Valgrind • Performance • Quantify (Available Soon) • Kcachegrind

22. Developer Tools • Test Coverage • Purecov (Available Soon) • Gcov • Scripting Language • Perl, Tcl/Tk, Python, JavaScript

23. GUI Development • Native GUI toolkits available • Gnome GTK+ is a C based public domain toolkit • LessTiff is Motif compatible library • Tcl/Tk provides scripting type capabilities • Java, AWT or Swing • Qt is a C++ class library commercially available from Trolltech • KDE is written in Qt • Portable across Linux/Unix/Windows platforms • Public Domain version available • Synopsys standardized on Qt

24. Summary • The PC has given us fast, inexpensive hardware • Linux enables EDA on the PC • Enterprise Linux makes this a viable solution • Stability, Compatibility, Predictability • Linux is a winning platform for EDA! • For customers and developers