1. Debugging, Build and Version Control Rudra Dutta CSC 230 - Spring 2007, Section 001

2. Copyright Rudra Dutta, NCSU, Spring, 20072 Practical Considerations In a practical environment, code must be integrated, maintained, packaged, and coding is a team effort Debugging – In general, and specifically “debugging” with printf Building – Minimal build - such as with make Other more powerful tools as well Commenting – Sensible commenting - turning comments into documentation Distribution - building libraries Version control – Allow the process of software evolution to be itself maintainable

3. Copyright Rudra Dutta, NCSU, Spring, 20073 Debugging - General Generally, debugging should start with examination of logic – Investigate using tests with boundary conditions – “Observe before modify” Debugging tools such as gdb allows easy examination of variables while stepping through code – Sometimes integrated into IDE – Compiling options may be required – Irritating situation - bug goes away when compiled as debug “Debugging” with printf – Insert printf at various points in the code to observe values – Major value: forces separation of code into easily understood statements – Minor value: comparatively platform and tool independent

4. Copyright Rudra Dutta, NCSU, Spring, 20074 Commenting First line of documentation With auto-generation, can effectively become nearly complete documentation – Auto-generating tools available, such as Doxygen – Similar to other language platforms, nothing specific to C Every function should document – Function call interface – Change to globals – Other side-effects on arguments – Forbidden calls – Boundary conditions – Sample calls – Author, modifier, date,...

5. Copyright Rudra Dutta, NCSU, Spring, 20075 Building Libraries Object files, one of which contains a main(), can be linked together to produce an executable Object files, none of which contains a main(), can also be archived together to produce a shared archive, or “library” Use the ar utility or equivalent Convention: “name” of archive is used (in slightly different ways) to find archive – Actual file will be called lib.a – Linked by gcc -l … – Needs to be in /usr/lib – Can be overridden by -L option

6. Copyright Rudra Dutta, NCSU, Spring, 20076 Archive Random Access A table of contents must be added before the library can be used – ranlib Another utility: libtool – Migrating to libtool on many platforms – Intended to replace both ar and ranlib – But check behavior Important to understand: – At the borderline between language and OS – For example: what is the format of binaries and object files?

7. Copyright Rudra Dutta, NCSU, Spring, 20077 Static and Dynamic Link Properly, an OS topic Multiply defined terms, various contexts For our purposes: – libtool or equivalent can produce libraries suitable for dynamic linking and/or loading However, may need support from compiler producing object files

8. Copyright Rudra Dutta, NCSU, Spring, 20078 Version Control Keep multiple programmers working on a project from clobbering each other Check out file - write ownership – Read-only access remains to others Check in modified copy - creates another version – May create complete version of code Can check out back versions CMVC, CVS, Subversion