Do I need -D_REENTRANT with -pthreads?
On Linux (kernel 2.6.5) our build system calls gcc with -D_REENTRANT. Is this still required when using pthreads? How is it related to gcc -pthread option? I understand that I should use -pthread with pthreads, do I still need -D_REENTRANT? On a side note, is there any difference that you know off between the usage of REENTRANT between gcc 3.3.3 and gcc 4.x.x ? When I use -pthread gcc option I can
Lseek implementation
Hi everybody, i've been googling for ages now and gotten kinda desperate... The question, however, might be rather trivial for the experts: What is it exactly, i.e. physically, the POSIX function (for a file) "lseek" does? Does it trigger some kind of synchronization on disk? Is it just for the file system? Rationale: I'm am running some benchmarks to get an idea, how our system (ext4@Debian5) wor
Man page of SYSCONF
Section: Linux Programmer's Manual (3) Updated: 2019-05-09 Index JM Home Page roff page åå‰ sysconf - 動作ä¸ã«è¨å®šæƒ…å ±ã‚’å–å¾—ã™ã‚‹ æ›¸å¼ #include <unistd.h> long sysconf(int name); 説明 POSIX ã§ã¯ã€ã‚¢ãƒ—リケーションãŒã‚³ãƒ³ãƒ‘イル時や実行時ã«ã€ 特定ã®ã‚ªãƒ—ションãŒã‚µãƒãƒ¼ãƒˆã•ã‚Œã¦ã„ã‚‹ã‹ã‚„〠è¨å®šå¯èƒ½ãªç‰¹å®šã®å®šæ•°ã‚„åˆ¶é™ (limits) ãŒã©ã‚“ãªå€¤ã‹ã‚’テストã™ã‚‹ã“ã¨ãŒã§ãる。 コンパイル時ã«è¡Œã†ã«ã¯ã€ <unistd.h> 㨠<limits.h> ã®ä¸¡æ–¹ã‚‚ã—ãã¯ä¸€æ–¹ã‚’インクルードã—〠特定ã®ãƒžã‚¯ãƒã®å€¤ã‚’確èªã™ã‚‹ã€‚ 実行時ã«ã¯ã€ã“ã“ã§èª¬æ˜Žã™ã‚‹é–¢æ•° sysconf() を使ã£ã¦æ•°å€¤ã‚’å•ã„åˆã‚ã›ã‚‹ã“ã¨ãŒã§ãる。 ファイルãŒå˜åœ¨ã™ã‚‹ãƒ•ã‚¡ã‚¤ãƒ«ã‚·ã‚¹ãƒ†ãƒ ã«ä¾å˜ã™
Posix共有メモリ - s-kita’s blog
Posix.1ã§ã¯ã€ç„¡é–¢ä¿‚ãªãƒ—ãƒã‚»ã‚¹é–“ã§ã®ãƒ¡ãƒ¢ãƒªå…±æœ‰ã‚’è¡Œã†æ–¹æ³•ã‚’２種類æä¾›ã—ã¦ã„る。 1.メモリマップファイル(memory-mapped files): ファイルをopenã—ã€çµæžœã®ãƒ•ã‚¡ã‚¤ãƒ«ãƒ‡ã‚£ã‚¹ã‚¯ãƒªãƒ—ã‚¿ã‚’mmapã§ãƒ—ãƒã‚»ã‚¹ã®ã‚¢ãƒ‰ãƒ¬ã‚¹ç©ºé–“ã«ãƒžãƒƒãƒ—ã™ã‚‹ 共有メモリオブジェクト(shared memory objects): shm_openã§IPCåをオープンã—ã€è¿”ã•ã‚ŒãŸãƒ‡ã‚£ã‚¹ã‚¯ãƒªãƒ—ã‚¿ã‚’mmapã§ãƒ—ãƒã‚»ã‚¹ã®ã‚¢ãƒ‰ãƒ¬ã‚¹ç©ºé–“ã«ãƒžãƒƒãƒ—ã™ã‚‹ shm_open関数ã€shm_unlink関数Posix共有メモリã®ä½¿ç”¨ã«ã¯ã€ï¼’ステップã®å‡¦ç†ãŒå¿…è¦ã€‚ 1.åå‰å¼•æ•°ã‚’与ãˆã¦shm_openを呼ã³å‡ºã™ 2.mmapを呼ã³å‡ºã—ã€å…±æœ‰ãƒ¡ãƒ¢ãƒªã‚’呼ã³å‡ºã—ãŸãƒ—ãƒã‚»ã‚¹ã®ã‚¢ãƒ‰ãƒ¬ã‚¹ç©ºé–“ã«ãƒžãƒƒãƒ—ã™ã‚‹ shm_openã§ç”¨ã„ãŸåå‰å¼•æ•°ã¯ã€ã“ã®ãƒ¡ãƒ¢ãƒªã‚’ä»–ã®ãƒ—ãƒã‚»ã‚¹ã‹ã‚‰å…±æœ‰ã™ã‚‹å ´åˆã«ç”¨ã„ã‚‹åå‰ã«ãªã‚‹ã€‚ #include <sys/mm
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