linux.txt

PROBLEMS/BUGS (LINUX/CYGWIN):
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
? build.sh: timing info format incorrect (linux) -- 31.01.2006: all OK?!
- linux testapp.cpp display warning about gets(); cygwin - no warning! (linker message)
! libs.a/libs.lib: should change name to contain platform name, add linux to libs/build.sh

GCC 4.0+ BUGS:
~~~~~~~~~~~~~
- (4.1:exists) when creating mapfile, names not demangled
  * demangling was moved from "ld" to "syminfo/make"
- (4.1:exists) visibility: `#pragma GCC visibility' not affects builtin functions, so - conflicts ... (displays warnings about
  trying to hide built-in visible function `operator new')
  - should use "-fvisibility..." cmdline instead of "#pragma GCC visibility ..."; make auto-detect of gcc4 from makefile:
    GCC_VER = $(shell echo __GNUC__ | gcc -E -xc - | tail -n 1)
    # also: __GCC_MINOR__
    ifeq ($(GCC_VER),4) / ifneq () ... (no -gt/-lt etc -- should use $(shell if [...] ...;))
- (4.1:exists) inlining: not inlined most of functions (can check with `-Winlines') - compiler says 'max-inline-insns-single reached',
  which, by info page, should be inline-limit/2 (by default, inline-limit=600 -- by info page)
  * may be fixed by inserting `--finline-limit=600', which is default (by documentation) value (should be automatic!)
  NOTE: inlining required for `operator new' and similar functions to take advantage of `mem_dump' console functions --
    * fixed using FORCEINLINE; other inline functions not inlined anyway (-Winline)!

------- REQUIREMENTS --------
min GCC version: 3.4.0
  3.3.2 have no:
    -Wno-invalid-offsetof
    - error in Core/Strings.h with PRINTF() macro?
    ... not tested more


TODO:
~~~~~
- fast math - make ability to turn off with #define (for debug; may be, GCC optimizes good by self ...)
- floor/ceil/round: not so fast ... (check GCC FAST_MATH ...); appRound() via lrint() rounds 2.5 and 4.5 to 3 (same as VC ...)
- assert(cond) or UT-like check() and verify()
- special code to test fast math functions (appRsqrt, appFloor, IsNegative, FAbsSign, ...) -- exec function + compare with non-fast
  equalent; allow small error; exec inside loop to disallow compile-time computations (either iterate values, or use table ...)


GCC TODO:
~~~~~~~~~
? mingw32 exception system (used exception/signal -> C++ throw before ...); currently uses setjmp() exception path (does works,
  but cannot catch "error -stack" -- mingw32/cygwin problem -- no separate signal stack)
- may be, access to SDK/includes from src as '#include <*>' instead of '#include "*"'
- asm constructions:
  - check floor/ceil/round (implement asm? check mingw math.h header for some details)
! compare VC/GCC speed (after floor/ceil/round -> GCC asm)
- "-ffunction-sections" slightly increase exe size; "-fdata-sections" grow q2 executable size up to 5 Mb ?!
- structure copy (for CVec3) is per-element (not memcpy())


To port application to Linux require following steps:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* port Core/*Win32.cpp
* exception hook: use signal() functions
* compile TestApp
- make net_wins.cpp cross-platform (initial: can create "empty" net device with loopback caps)
  ! should redesign networking lower level unit
- create sys_win.cpp for Linux
  ? may be, create set of MainLoop wrappers in Core headers -- or set of main()/WinMain() functions, and app should
    provide MainLoop() only?
- compile dedicated server (1.cygwin 2.linux)
- verify network compatibility with Win32
- ...
- create empty sound driver, use it for "nosound=1" (?)
- port input+windowing -> SDL (may use cygwin+sdl !)
- ...
- separate sound driver from client code
- create OpenAL sound driver, use for win32 too
? may be, create SDL sound driver too (in a case of absece OpenAL library)
- ...


To allow binaries to work under any Linux version/distribution:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- use static linkage with C++ libraries (libstdc++.so.6 etc)
  - libstdc++.so: should be dynamic to allow inter-module exceptions (not used here)
  * tried linux of 2001 year (kernel 2.2, KDE 2.1, libc is v6) -- libc.so.6 requires LIBC2_... exports
    (so - build with static libc too? -- or static/shared versions?)
  ? may be, do not need to support old linux versions - build for current versions, but ensure, upgrading linux
    will not break binary/library compatibility
- may be, statically link with all modules (app and system)


GCC notes:
~~~~~~~~~~
* appGetSystemErrorMessage() -- strerror(code)
* #pragma(pack...) -- struct name __attribute__((__packed__)) {}
  (note: may use __attribute__((packed)) instead
- function attributes:
  - warn_usused_result - warning, when result of function ignored
  - constructor/destructor - call function before main()/exit()
  - format_arg(index) - arg #index is printf-like format specifier
- DLL_IMPORT/DLL_EXPORT:
  * use __attribute__((visibility))
  - check "dsohowto.pdf" chapter 2.2 (seems, require GCC 4+ or patched compiler)
  - check misc/compilers/GCC_Visibility.htm
- varargs in macros (see GCC doc 5.15)
- type_t varName; "typeof(varName) varName2" == "type_t varName2"
- __func__ macro: "const char name[]" of current function
- i386 type attribute: ms_struct, gcc_struct
- to create dynamic build: use "ld -rpath ..." cmdline arg to allow placing engine .so files into non-standard dirs

----------------------------------------------------------

"Proc" file system:
* /proc/version -- OS version (can use uname())
  /proc/cpuinfo -- CPU information (can use for non-x86 or when no CPUID support)
* /proc/%d      -- some process information (%d == pid); can use "self" instead of %d
    cmdline     -- very similar to argv[]; useless for self (but may be used to obtain cmdlines of other processes)
*   exename
*   maps        -- which exe/dll/so loaded (2.4); WARNING: linux and cygwin have different "offset" meaning! (cygwin => entry point)