Programming Links and Insights

cc.md

Phases

Preprocessing phase

• basic source character set (no `$@) translated to universal character name (\u + \U)
• (trigraph sequences)
• <newline> at the end of the line are removed (single pass)
• decomposed into comments and preprocessing tokens:
  • header names, identifiers, numbers, literals, etc.
  • operators + punctuators
• transformations inside double quotes are reverted
• each comment replaced by a single space
• preprocessor executed -> all preprocessor tokens are removed

Compilation phase

• literals are converted from source character set to execution character set
• adjacent string literals are concatenated
• ��compilation executed (syntactic analyzation and semantic analyzation)

Linking phase

• each TU examined to procude list of template instantiations
• definitions of templates and required instantiants are perfromed to produce instantiation units (IU)
• TUs, IUs, and libraries needed to satisfy external references are collected into program image
• linking takes place

Clang compilation

• -target-cpu core2

• -target-linker-version 253.9

• -dwarf-column-info

• -fdebug-compiliation-dir $CURDIR

• -ferror-limit "19"

• -fmessage-length "135"

• -munwind-tables

• -mrelax-all

• -mrelocation model pic -pic_level

• -mthread-model posix

• -mdisable-fp-elim

• -masm-verbose

• -Wdeprecated=obj-isa-usage

• -Werror=obj-isa-usage

• -main-file-name 'a.c'

Clang++ compilation

• • -lc++
• • -stdlib=c++
• • -fdeprecated=macro
• • -fcxx_exception
• • -fexceptions

• -E : preprocessing

• -f : syntax only

• -S : assembly code (GA)

• -c : normal compilation

Differences between C and C++

1. implicit assignment from void* in C in C: always cast the result to the corresponding type (e.g. int *ptr = (int*) malloc(sizeof(int)); )
2. string literals are char[] in C, char const[] in C++ in C: always assign string literals to char const[], instead of char[]
3. new + new[] instead of malloc, calloc, etc. Nothing you can do about it, avoid malloc in C++
4. necessity of declaration of function before use in C++ do that in C as well
5. typedef vs. using
6. always return from main -> it's just a function!
7. in C, main is callable from other functions, but don't do it
8. don't skip initializations in C
9. Avoid tentative definitions in C
10. Don't declare tags in C function prototypes
11. don't cast implicit const to non-const
12. always initialize const values (not necessary in C++)
13. char constant int in C, char in C++
14. const globals are file scope in C, not in C++

clang shared libraries

• @executable_path: relative to directory of main executable
• @loader_path: relative to referring library -> for plug-ins
• @rpath: relative to any list of paths which are passed as arguments when compiling (-rpath)

linux.md

Linux

pthread_mutex_t _init _lock _unlock _destroy _trylock

pthread_condattr _init _destroy pthread_cond _init _destroy _signal _wait _timedwait _broadcast

rwlock _init _destroy _rdlock _wrlock _tryrdlock _trywrlock _unlock

each INODE consists of:

• file type (regular file, directory, block device file, etc.)
• number of hardlinks associated
• file length in bytes
• device ID
• inode that identifies the file
• UID
• GID
• atime, mtime and ctime
• access rights + file mode

apt-cache

• stats: shows general stats about pkgs
• gencaches: build both package and source
• show: show a readable record for package
• showpkg: show general information for pkg
• showsrc: show source records
• search
• depends: all dependencies
• rdepends: all reverse dependencies
• unmet: all unmet depen