C言語ã®bitfieldã®ä»•æ§˜ã¨å®Ÿè£…を調査ã—ãŸè©± - /home/tnishinaga/TechMEMO
C言語ã«ã¯bitfieldã¨ã„ã†æ©Ÿèƒ½ãŒã‚ã‚Šã¾ã™ãŒã€ã“ã®æ©Ÿèƒ½ã«ã¯ã•ã¾ã–ã¾ãªè½ã¨ã—ç©´ãŒã‚ã‚Šã€æ³¨æ„æ·±ã利用ã—ã¦ã‚‚予期ã›ã¬ãƒã‚°ã‚„移æ¤æ€§ã®å•é¡Œã‚’引ãèµ·ã“ã™å¯èƒ½æ€§ãŒã‚ã‚‹ã¨ã‚ˆã言ã‚ã‚Œã¦ã„ã¾ã™ã€‚ 実際ã€jpcertを確èªã™ã‚‹ã¨è¤‡æ•°ã®å‹§å‘ŠãŒå‡ºã¦ã„ã¾ã™ã€‚ EXP11-C. ãƒ“ãƒƒãƒˆãƒ•ã‚£ãƒ¼ãƒ«ãƒ‰æ§‹é€ ä½“ã®ãƒ¬ã‚¤ã‚¢ã‚¦ãƒˆã«ã¤ã„ã¦å‹æ‰‹ãªæƒ³å®šã‚’ã—ãªã„ INT12-C. å¼ä¸ã§ä½¿ç”¨ã•ã‚Œã‚‹å˜ãªã‚‹intã®ãƒ“ットフィールドã®åž‹ã«ã¤ã„ã¦å‹æ‰‹ãªæƒ³å®šã‚’ã—ãªã„ CON32-C. 複数スレッドã«ã‚ˆã‚‹éš£æŽ¥ãƒ‡ãƒ¼ã‚¿ã¸ã®ã‚¢ã‚¯ã‚»ã‚¹ãŒå¿…è¦ãªå ´åˆãƒ‡ãƒ¼ã‚¿ç«¶åˆã‚’防æ¢ã™ã‚‹ DCL39-C. ä¿¡é ¼å¢ƒç•Œã‚’è¶Šãˆã¦æ§‹é€ 体を渡ã™ã¨ãæƒ…å ±æ¼ãˆã„ã—ãªã„ ç§ã¯å…ˆè¼©æŠ€è¡“者ã‹ã‚‰ã€Œã¨ãã«çµ„ã¿è¾¼ã¿ã®åˆ†é‡Žã«ãŠã„ã¦C言語ã®bitfieldã¯ä½¿ã†ã¹ãã§ã¯ãªã„ã€ã¨æ•™ã‚ã£ã¦ç”Ÿãã¦ãã¾ã—ãŸã€‚ 本記事ã§ã¯bitfieldã®ä»•æ§˜ã‚„å•é¡Œç‚¹ã€ãªãœä»•æ§˜ã‚’é¿ã‘ã‚‹ã¹ãã‹ã€ç·©å’Œç–や代替案ã«ã¤ã„ã¦æ¤œè¨Žã—ã¾ã™ã€‚ 目次
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å›žç” (31件ä¸ã®1件目) C ã®ä¸‹ã«ã‚る仕組を知らãšã«è¦šãˆã‚ˆã†ã¨ã™ã‚‹ã‹ã‚‰ã€é›£ã—ã„ã®ã ã¨æ€ã„ã¾ã™ã€‚ ç§ã¯ã€å¤§å¦ã®å°‚門課程ã®å®Ÿé¨“㧠8bit ã®æ©Ÿæ¢°èªžã‚’実体験ã—ãŸå¾Œã€ã‚¢ã‚»ãƒ³ãƒ–リ言語を経㦠C ã«åˆ°é”ã—ã¾ã—ãŸã€‚メモリã®ã‚¢ãƒ‰ãƒ¬ã‚¹ã‚’æ„è˜ã—ãªã„ã¨ä½•ã‚‚ã§ããªã„世界を知ã£ã¦ã„ãŸè¨³ã§ã™ã€‚ 一方ã§ã€é«˜ç´šè¨€èªžã¯ Fortran (パンãƒã‚«ãƒ¼ãƒ‰!) ã‹ã‚‰å…¥ã‚Šã¾ã—ãŸã€‚ ãã“ã‹ã‚‰ C ã«å…¥ã‚‹ã¨ã€ 1. ç—’ã„所ã«æ‰‹ãŒå±Šã (ãƒã‚¤ãƒ³ã‚¿ãŒæ‰±ãˆã‚‹) 2. 算術演算å㧠10 進計算ãŒã§ãã‚‹ ã¨ã„ã†ä¸æ€è°ãªè¨€èªžã«è¦‹ãˆã¾ã—ãŸã€‚低級ãªã‚“ã ã‹é«˜ç´šãªã‚“ã ã‹ã€ã‚ã‹ã‚‰ãªã„。 慣れã¦ãã‚‹ã¨ã€ã»ã¨ã‚“ã©ã®é«˜ç´šãªæ“作ã¯æ¨™æº–関数を使ã£...
The state of static analysis in the GCC 12 compiler | Red Hat Developer
Building a static analyzer into the C compiler offers several advantages over having a separate tool, because the analyzer can track what the compiler and assembler are doing intimately. As a Red Hat employee, I work on GCC, the GNU Compiler Collection. Our static analyzer is still experimental but is making big strides in interesting areas, including a taint mode and an understanding of assembly-
Are GCC and Clang parsers really handwritten?
It seems that GCC and LLVM-Clang are using handwritten recursive descent parsers, and not machine generated, Bison-Flex based, bottom up parsing. Could someone here please confirm that this is the case? And if so, why do mainstream compiler frameworks use handwritten parsers? Update : interesting blog on this topic here
Continuation based Cを試㙠- Qiita
Continuation based Cã¨ã¯ 以下ã€é•·ã„ã®ã§ç•¥ç§°ã®CbCã¨æ›¸ãã¾ã™ã€‚ 状態é·ç§»è¨˜è¿°ã«å‘ã„ãŸãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°è¨€èªž CbC ã®é–‹ç™º C 言語ã«ãŠã‘る関数呼ã³å‡ºã—ã‚„for 文・while 文を排除ã—，状態é·ç§»å˜ä½(code) ã§ã®å‡¦ç†ã‚’記述ã§ãる言語ã®é–‹ç™ºã‚’ã—ã¦ã¾ã™ï¼Ž https://ie.u-ryukyu.ac.jp/%E5%AD%A6%E7%A7%91%E7%B4%B9%E4%BB%8B/%E7%A0%94%E7%A9%B6%E5%AE%A4%E7%B4%B9%E4%BB%8B/%E4%B8%A6%E5%88%97%E7%A0%94%E7%A9%B6%E5%AE%A4%EF%BC%88%E6%B2%B3%E9%87%8E%E7%A0%94%EF%BC%89/ 詳ã—ãã¯ã“ã®è¾ºã®è«–文をèªã‚€ã¨ã‚ˆã•ãㆠhttp://www.ie.u-ryukyu.ac.jp/~kono/papers
64C/128Tã®ã€ŒRyzen Threadripper 3990Xã€ã®ãƒ‘ワーãŒLinuxã§ã©ã“ã¾ã§æ´»ãã‚‹ã‹æ¤œè¨¼ (2/2)
Apache以外ã¯ã©ã‚Œã‚‚コア数ãŒå¤šã„æ–¹ãŒé€Ÿãã€ç‰¹ã«Ryzen Threadripperå‹¢ã¯LLVMã‚„Linuxカーãƒãƒ«ã®ãƒ“ルドã«ãŠã„ã¦åœ§å€’çš„ã«é€Ÿã„。ãŸã ã€Ryzen Threadripper 3990Xã¯é€Ÿã„ã“ã¨ã¯ç¢ºã‹ã ãŒã€3970Xã«å¯¾ã—ã¦åœ§å€’çš„ã‹ã€ã¨è¨€ã‚れるã¨å›žç”ã«è‹¦ã—む。gccã®ã‚³ãƒ³ãƒ‘イル時間ã§ã¯ãã‚ŒãŒé¡•è‘—ã 。 ãŸã ã€å·¨å¤§ãªã‚½ãƒ¼ã‚¹ã‹ã‚‰ä½•åº¦ã‚‚ビルドã™ã‚‹ã‚ˆã†ãªçŠ¶æ³ã§ã¯ã€1秒ã§ã‚‚æ—©ãå¾…ã¡æ™‚é–“ã‚’çŸç¸®ã™ã‚‹ãŸã‚ã«Ryzen Threadripper 3990Xã¨ã„ã†é¸æŠžè‚¢ã¯ã‚ã‚Šã‹ã‚‚ã—ã‚Œãªã„。最も時間ã®ã‹ã‹ã‚‹8C16Tã®Ryzen 7 3800Xã‹ã‚‰ä¹—ã‚Šæ›ãˆã‚‹ã¨ä»®å®šã™ã‚‹ã¨ã€12C24Tã®3900Xã«ä¹—ã‚Šæ›ãˆã‚‹ã ã‘ã§ã‚¸ãƒ£ãƒ³ãƒ—アップãŒæ„Ÿã˜ã‚‰ã‚Œã‚‹ãŒã€Ryzen Threadripper環境ã ã¨çµ¶å¤§ãªåŠ¹æžœã‚’得られるãŒã€ãƒ“ルドã™ã‚‹å¯¾è±¡ã«ã‚ˆã‚Šã‚¸ãƒ£ãƒ³ãƒ—アップ率ã¯å¤§ãã変ã‚ã‚‹ã¨ã„ã£ãŸã¨ã“ã‚ã 。 最後ã«ãŠã¾ã‘ã¨ã—ã¦
KMC Staff Blog:GCC10ã®æœ€é©åŒ–ã«ã‚ˆã‚‹memsetã§ã®ç„¡é™ãƒ«ãƒ¼ãƒ—ã®ç™ºç”Ÿ
2020å¹´11月17æ—¥ GCC10ã®æœ€é©åŒ–ã«ã‚ˆã‚‹memsetã§ã®ç„¡é™ãƒ«ãƒ¼ãƒ—ã®ç™ºç”Ÿ 以å‰ã€ã€ŒGCCã®æœ€é©åŒ–ã«ã‚ˆã‚‹äºˆæœŸã›ã¬ç„¡é™ãƒ«ãƒ¼ãƒ—ã®ç™ºç”Ÿã€ã¨ã„ã†è¨˜äº‹ã‚’書ãã¾ã—ãŸã€‚ã“ã®æ™‚㯠-fno-builtin-malloc ã‚„ __asm __volatile("":::"memory"); ãªã©ã§å¯¾ç–ã§ãã¾ã—ãŸã€‚ ã—ã‹ã—今回ã€ç¾çŠ¶æœ€æ–°ã® GCC 10 ã§ã€memsetã€ã—ã‹ã‚‚ナイーブ㪠*(char *)s++ = (char)c; ã¿ãŸã„ãªå®Ÿè£…ã§ã¯ãªãã€NetBSD ã®æœ¬æ ¼çš„ãªå®Ÿè£…ã®ã‚‚ã®ã§ç™ºç”Ÿã—ã€-fno-builtin ã‚„ -fno-builtin-memsetã€-ffreestanding ãªã©ã§ã‚‚抑制ã§ããšã€-fno-tree-loop-distribute-patterns ã¨ã„ã†ã‚ã¾ã‚Šä¸€èˆ¬çš„ã§ã¯ãªã„オプションãŒå¿…è¦ã«ãªã‚Šã¾ã—ãŸã€‚ ã“ã‚Œã¯ä¸€è¦‹ GCC ã®ã‚ªãƒ—ションãŒåŠ¹ã„ã¦ãªã„ã€ãƒã‚°ã®ã‚ˆã†ã«æ€
2020å¹´8月26日　Linuxカーãƒãƒ«ã€ç´„2500ã®"フォールスルー"をリプレース | gihyo.jp
Linus Torvaldsã¯8月24日（米国時間â ）â ã€2020å¹´10月ã®ãƒªãƒªãƒ¼ã‚¹ã«å‘ã‘ã¦é–‹ç™ºä¸ã®ã€ŒLinux 5.9ã€ã«ãŠã„ã¦ã€ã‚«ãƒ¼ãƒãƒ«ã‚¨ãƒ³ã‚¸ãƒ‹ã‚¢ã®Gustavo Silvaã®ä¿®æ£ãƒ‘ッãƒã‚’マージã—ãŸã€‚ã“ã®ãƒ‘ッãƒã§ã¯ã‚«ãƒ¼ãƒãƒ«å…¨ä½“ã§ä½¿ã‚ã‚Œã¦ã„ãŸ2484ã‚‚ã®ã€Œ/* fall through */ã€ãŠã‚ˆã³é¡žä¼¼ã®ã‚³ãƒ¡ãƒ³ãƒˆéƒ¨åˆ†ã‚’ã™ã¹ã¦ã€Œfallthrough;ã€ã«ãƒªãƒ—レースã—ã¦ã„ã‚‹ã»ã‹ã€ä¸è¦ãªfall-throughã®å‰Šé™¤ã‚‚è¡Œã‚ã‚Œã¦ã„る。 Merge tag 'fallthrough-pseudo-keyword-5.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux -Linux kernel source tree Linuxカーãƒãƒ«ã®ãƒ¡ã‚¤ãƒ³ãƒ©ã‚¤ãƒ³é–‹ç™ºã§ã¯ã€ä»Šå›žã®ãƒ‘ッãƒã‚’æä¾›ã—ãŸSilvaã‚’ä¸å¿ƒã«ã€s
x64 Assembly Language Programming
汎用レジスタãŒå€å¢—ã—ãŸã®ã§å¼•æ•°ã®æ•°ãŒå°‘ãªã„ã¨ãã¯ã‚¹ã‚¿ãƒƒã‚¯çµŒç”±ã§ã¯ãªã基本的ã«ãƒ¬ã‚¸ã‚¹ã‚¿çµŒç”±ã«ãªã‚Šã¾ã—ãŸ. ã¾ãŸ32bitã®ã¨ãã«ã‚ã£ãŸ__fastcall, __stdcallãªã©(cf. VC++ã§ã¯)ã¯å…¨ã¦ç„¡è¦–ã•ã‚Œã‚‹ã‚ˆã†ã«ãªã‚Šã¾ã—ãŸ. C++ã®ãƒ¡ãƒ³ãƒé–¢æ•°ã®å‘¼ã³å‡ºã—方法ã«ã¤ã„ã¦ã¯C++ã§ã¯ã‚’å‚ç…§. Cã®é–¢æ•°ã®ãƒ¬ã‚¸ã‚¹ã‚¿ã®ä½¿ã„æ–¹ã¯æ¬¡ã®é€šã‚Šã§ã™. レジスタã®ç”¨é€” レジスタ 用途 呼ã³å‡ºã•ã‚ŒãŸå´(callee)ã§ã®ä¿å˜ã®å¿…è¦æ€§ rax 戻り値 ä¸è¦ rcx 1番目ã®æ•´æ•°åž‹å¼•æ•° ä¸è¦ rdx 2番目ã®æ•´æ•°åž‹å¼•æ•° ä¸è¦ r8 3番目ã®æ•´æ•°åž‹å¼•æ•° ä¸è¦ r9 4番目ã®æ•´æ•°åž‹å¼•æ•° ä¸è¦ r10, r11 - ä¸è¦ r12～r15, rdi, rsi, rbx, rbp, rsp - 変更ã™ã‚‹ãªã‚‰å¿…è¦* xm0 1番目ã®æµ®å‹•å°æ•°åž‹å¼•æ•° / 戻り値 ä¸è¦ xm1 2番目ã®æµ®å‹•å°æ•°åž‹å¼•æ•° ä¸è¦ xm2 3番目ã®
KMC Staff Blog:GCCã®æœ€é©åŒ–ã«ã‚ˆã‚‹äºˆæœŸã›ã¬ç„¡é™ãƒ«ãƒ¼ãƒ—ã®ç™ºç”Ÿ
2019å¹´09月13æ—¥ GCCã®æœ€é©åŒ–ã«ã‚ˆã‚‹äºˆæœŸã›ã¬ç„¡é™ãƒ«ãƒ¼ãƒ—ã®ç™ºç”Ÿ コンパクトãªç‹¬è‡ªã® libc を実装ã—ã¦ã„ã¦ã€GCC ã®ãƒ†ã‚¹ãƒˆã‚’通ã—ãŸã¨ã“ã‚ã€WARNING: program timed out. ãŒåŽŸå› ã«ã‚ˆã‚‹ FAIL ãŒå¤šç™ºã—ã¾ã—ãŸã€‚調ã¹ãŸçµæžœã€éžå¸¸ã«æ„外ãªçµæžœã ã£ãŸã®ã§ãƒ¡ãƒ¢ã—ã¾ã™ã€‚ å•é¡Œã¯ã€calloc ã®å®Ÿè£…ã§ã—ãŸã€‚以下ã®ã‚ˆã†ã«ã€å…¨ãå•é¡Œç„¡ã•ãã†ãªç°¡å˜ãªã‚³ãƒ¼ãƒ‰ã§ã™ã€‚ #include <stdlib.h> #include <string.h> void *calloc(size_t n, size_t size) { size_t bytes = n * size; void *p = malloc(bytes); if (p) { memset(p, 0, bytes); } return p; } ã“ã‚ŒãŒã€GCC 6.4.0 ã® arm-eabi 㧠O2 ã§ã‚³ãƒ³ãƒ‘イル
GCCã®æœ€é©åŒ– - Gentoo wiki
ã¯ã˜ã‚ã« CFLAGS 㨠CXXFLAGS ã¨ã¯ï¼Ÿ CFLAGSã¨CXXFLAGSã¯ã€Cã‚„C++ã®ã‚½ãƒ¼ã‚¹ã‚³ãƒ¼ãƒ‰ã‚’コンパイルã™ã‚‹ã¨ãã«ä½¿ã‚れるオプションをã€ã‚³ãƒ³ãƒ‘イラã«æŒ‡ç¤ºã™ã‚‹ãŸã‚ã«æ…£ä¾‹çš„ã«ä½¿ã‚れる環境変数ã®ä¸€ç¨®ã§ã™ã€‚ã“れらã®ç’°å¢ƒå¤‰æ•°ã¯æ¨™æº–化ã•ã‚Œã¦ã„ã‚‹ã‚ã‘ã§ã¯ã‚ã‚Šã¾ã›ã‚“ãŒãã‚Œã«è¿‘ã„状æ³ã§ç”¨ã„られã¦ãŠã‚Šã€ã‚³ãƒ³ãƒ‘イラを使ã†éš›ã«è¿½åŠ ã®ã‚ªãƒ—ションを指定ã—ãŸã„ãªã‚‰ç†è§£ã—ã¦ãŠãå¿…è¦ãŒã‚ã‚Šã¾ã™ã€‚GNU makeã§ã¯ä¸€èˆ¬çš„ã«ã‚ˆã使ã‚ã‚Œã¦ã„る環境変数ã®ãƒªã‚¹ãƒˆãŒè¨˜ã•ã‚Œã¦ã„ã¾ã™ã€‚ Gentooシステムã§ã¯å¤§å¤šæ•°ã®ãƒ‘ッケージãŒCã¾ãŸã¯C++ã§æ›¸ã‹ã‚Œã¦ã„ã‚‹ãŸã‚ã€ã“れらã®ç’°å¢ƒå¤‰æ•°ã¯ã‚·ã‚¹ãƒ†ãƒ ãŒã©ã®ã‚ˆã†ã«æ§‹æˆã•ã‚Œã‚‹ã‹ã«å¤šå¤§ãªå½±éŸ¿ã‚’åŠã¼ã—ã¾ã™ã€‚ãã®ãŸã‚管ç†è€…ã«ã¯ã“れらをæ£ã—ãè¨å®šã™ã‚‹ã“ã¨ãŒæ±‚ã‚られã¾ã™ã€‚ ã“れらã¯ãƒ—ãƒã‚°ãƒ©ãƒ ã®ãƒ‡ãƒãƒƒã‚°ãƒ¡ãƒƒã‚»ãƒ¼ã‚¸ã®é‡ã‚’減らã™ãŸã‚ã«ä½¿ã‚ã‚ŒãŸã‚Šã€ã‚¨ãƒ©ãƒ¼ã‚„è¦å‘Šã®ãƒ¬ãƒ™ãƒ«ã‚’å¢—åŠ ã•ã›ãŸã‚Šã€ã¾ãŸã€ã‚‚ã¡ã‚ん生
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