{"id":2627,"date":"2020-11-25T10:24:00","date_gmt":"2020-11-25T01:24:00","guid":{"rendered":"http:\/\/43.203.250.216\/?p=2627"},"modified":"2020-12-30T11:36:53","modified_gmt":"2020-12-30T02:36:53","slug":"gcc%ec%97%90%ec%84%9c-integer-arithmetic-overflow-%eb%b0%a9%ec%a7%80-%eb%8c%80%ec%b1%85","status":"publish","type":"post","link":"https:\/\/litcoder.com\/?p=2627","title":{"rendered":"GCC\uc5d0\uc11c integer arithmetic overflow \ubc29\uc9c0 \ub300\ucc45"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Arithmetic overflow\ub294 \ubd80\ud638 \uc788\ub294 \ubcc0\uc218(signed variable)\uac00 \ud45c\uc2dc \ud560 \uc218 \uc788\ub294 \ucd5c\ub313\uac12 \/ \ucd5c\uc19f\uac12\uc744 \ub118\uc5b4 \uc130\uc744 \ub54c \ubd80\ud638\uac00 \ubc14\ub00c\uba74\uc11c \uc6d0\ud558\uc9c0 \uc54a\ub294 \uacb0\uacfc\uac00 \ub098\ud0c0\ub098\ub294 \uacbd\uc6b0\ub97c \ub9d0\ud55c\ub2e4.<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"cpp\" data-enlighter-theme=\"eclipse\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;iostream>\n#include &lt;climits>\n\nusing namespace std;\nint main(void) {\n    int r = 0;\n    int op = INT_MAX;\n    cout &lt;&lt; op &lt;&lt; \" + 1 = \" &lt;&lt; op + 1 &lt;&lt; endl;\n    return 0;\n}<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uc704\uc758 \ucf54\ub4dc\ub97c \ub2e4\uc74c\uacfc \uac19\uc774 \ucef4\ud30c\uc77c\ud558\uace0 \uc2e4\ud589\ud558\uba74 overflow\uac00 \ubc1c\uc0dd\ud55c\ub2e4.<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"raw\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">$ g++ .\/overflow.cpp\n$ .\/a.out\n2147483647 + 1 = -2147483648<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uc774\uc640 \uac19\uc740 \uacbd\uc6b0\ub97c \ubc29\uc9c0 \ud558\ub824\uba74 \ubb3c\ub860 \uaf3c\uaf3c\ud55c \ucf54\ub4dc \ub9ac\ubdf0\ub3c4 \uc911\uc694 \ud558\uc9c0\uaca0\ub9cc \ucef4\ud30c\uc77c\ub7ec\uc5d0\uc11c \uc81c\uacf5\ud558\ub294 <a href=\"https:\/\/gcc.gnu.org\/onlinedocs\/gcc\/Integer-Overflow-Builtins.html\" data-type=\"URL\" data-id=\"https:\/\/gcc.gnu.org\/onlinedocs\/gcc\/Integer-Overflow-Builtins.html\">overflow\ub97c \uc810\uac80\ud558\ub294 \ube4c\ud2b8\uc778 \ud568\uc218<\/a>\ub97c \uc0ac\uc6a9\ud558\uac70\ub098 <a href=\"https:\/\/github.com\/dcleblanc\/SafeInt\" data-type=\"URL\" data-id=\"https:\/\/github.com\/dcleblanc\/SafeInt\">Safeint<\/a> \ud639\uc740 \uc774\uc640 \uc720\uc0ac\ud55c Boost\uc758 <a href=\"https:\/\/www.boost.org\/doc\/libs\/1_73_0\/libs\/safe_numerics\/doc\/html\/notes.html\" data-type=\"URL\" data-id=\"https:\/\/www.boost.org\/doc\/libs\/1_73_0\/libs\/safe_numerics\/doc\/html\/notes.html\">Safe numerics<\/a>\uc758 \uc0ac\uc6a9\uc744 \uace0\ub824\ud574 \ubcfc \uc218\ub3c4 \uc788\uaca0\ub2e4. \ud558\uc9c0\ub9cc \uc774 \ubc29\ubc95\ub4e4\uc740 \ucc98\uc74c\ubd80\ud130 \uc0ac\uc6a9\uc774 \uace0\ub824\ub418\uc5b4\uc57c \ud558\uac70\ub098 \uc774\ubbf8 \uc791\uc131\ud55c \ucf54\ub4dc\ub97c \uc218\uc815\ud574\uc57c \ud558\ub294 \ub2e8\uc810\uc774 \uc788\ub2e4.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">-ftrapv compiler switch<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">GCC \ucef4\ud30c\uc77c\ub7ec\uc5d0\uc11c \uc81c\uacf5\ud558\ub294 -ftrapv switch\ub97c \uc0ac\uc6a9\ud558\uba74 \ucf54\ub4dc \uc218\uc815 \uc5c6\uc774 arithmetic overflow\uac00 \ubc1c\uc0dd \ud588\uc744 \ub54c SIGABRT\ub97c \ubc1c\uc0dd \uc2dc\ud0a4\ub3c4\ub85d \ucef4\ud30c\uc77c\ub7ec\uac00 trap\uc744 \ucd94\uac00\ud558\uac8c \ud560 \uc218 \uc788\ub294\ub370, \ubc1c\uacac \ub418\uc9c0 \uc54a\uc740 overflow\ub97c \uc77c\uc73c\ud0a8 \ud6c4 \uc624\ub3d9\uc791\uc744 \ud558\uac8c \ub418\ub294 \uac83 \ubcf4\ub2e4\ub294 \ud504\ub85c\uc138\uc2a4 \uc911\ub2e8\uc774 \ub0ab\ub2e4\uace0 \uc0dd\uac01\ud558\uba74 \uc774 switch\ub97c  \uace0\ub824\ud574 \ubcfc \uc218 \uc788\ub2e4.<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"raw\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">$ g++ -ftrapv .\/overflow.cpp\n$ .\/a.out\nAborted (core dumped)<\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">-fwrapv compiler switch<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\ub610 \ub2e4\ub978 \uacbd\uc6b0\ub85c \ucd5c\uc801\ud654 \uc635\uc158\uc5d0 \ub530\ub77c \uc2e4\ud589 \uacb0\uacfc\uac00 \ub2ec\ub77c \uc9c0\ub294 \uacbd\uc6b0\ub3c4 \uc788\ub2e4. \ub2e4\uc74c\uc758 \uc608\uc81c\ub294 Stack overflow\uc758 <a href=\"https:\/\/stackoverflow.com\/questions\/47232954\/what-does-fwrapv-do\">What does -fwrapv do?<\/a>\ub97c \uc57d\uac04 \ubcc0\ud615\ud55c \uac83\uc774\ub2e4. <\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"cpp\" data-enlighter-theme=\"eclipse\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;iostream>\n#include &lt;climits>\n \nusing namespace std;\nint optFunc(int i) {\n    return i+1 > i;\n}\n \nint main(void) {\n    int v = INT_MAX;\n \n    if (optFunc(v)) {\n        cout &lt;&lt; \"Unexpected.\" &lt;&lt; endl;\n    } else {\n        cout &lt;&lt; \"Terminated OK.\" &lt;&lt; endl;\n    }\n\t\n    return 0;\n}<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\ud604\uc2e4\uc5d0\uc11c \uc4f0\uc77c \ubc95\ud55c \ucf54\ub4dc\ub294 \uc544\ub2c8\uc9c0\ub9cc optFunc()\ub97c \uc791\uc131\ud55c \uc0ac\ub78c\uc758 \uc758\ub3c4\uac00 INT_MAX\uac00 \uc778\uc790\ub85c \uc8fc\uc5b4\uc9c8 \ub54c &#8220;<strong>INT_MAX + 1<\/strong>&#8220;\uc774 \uc74c\uc218\uac00 \ub418\uba74\uc11c &#8220;INT_MAX + 1 &gt; INT_MAX&#8221;\uac00 <strong>false(0)<\/strong>\ub97c \ubc18\ud658\ud558\ub3c4\ub85d \ud558\ub294 \uac83\uc774\uc5c8\ub2e4 \ud558\ub354\ub77c\ub3c4 \uc774 \ucf54\ub4dc\ub294 \ucd5c\uc801\ud654 \uc635\uc158\uc5d0 \ub530\ub77c \ub2e4\ub978 \uacb0\uacfc \uac12\uc744 \ub0b4\uac8c \ub41c\ub2e4.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\ub514\ubc84\uae45 \ub4f1\uc758 \uc774\uc720\ub85c \ucef4\ud30c\uc77c \ud560 \ub54c \ucd5c\uc801\ud654\ub97c \uc635\uc158\uc744 -O0\ub85c \uc8fc\uba74 \uc6d0\ud558\ub294 \ub300\ub85c \ub3d9\uc791\ud55c\ub2e4.<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"raw\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">$ g++ -O0 .\/fwrapv.cpp\n$ .\/a.out \nTerminated OK.<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\ud558\uc9c0\ub9cc, -O3 \uc635\uc158\uc744 \uc8fc\uba74, \ucef4\ud30c\uc77c\ub7ec\ub294 optFunc()\uac00 \ud56d\uc0c1 true(1)\uc744 \ubc18\ud658 \ud560 \uac83\uc774\ub77c \uac00\uc815\ud558\uace0 \ucef4\ud30c\uc77c\ub7ec\uac00 \uc774\ub97c \ucd5c\uc801\ud654 \uc2dc\ucf1c \ubc84\ub824\uc11c \ucf54\ub4dc\uac00 \uc758\ub3c4\ud55c \ub300\ub85c \ub3d9\uc791\ud558\uc9c0 \uc54a\uac8c \ub41c\ub2e4.<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"raw\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">$ g++ -O3 .\/fwrapv.cpp\n$ .\/a.out \nUnexpected.<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uc774\ub7ec\ud55c \uacbd\uc6b0\ub97c \ubc29\uc9c0 \ud558\uae30 \uc704\ud574 -fwrapv switch\ub97c \uc8fc\uba74 -O3 \uc774\uc0c1\uc758 \ucd5c\uc801\ud654 \uc635\uc158\uc5d0\uc11c\ub3c4 \ud574\ub2f9 \ubd80\ubd84\uc774 &#8216;wrapping&#8217; \ub418\uc5b4\uc11c \uc758\ub3c4\ud55c \ub300\ub85c \ucf54\ub4dc\uac00 \ub3d9\uc791\ud558\uac8c \ub41c\ub2e4.<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"raw\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">$ g++ -O3 -fwrapv .\/fwrapv.cpp\n$ .\/a.out \nTerminated OK.<\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">-Wconversion compiler switch<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\ubcf4\ub2e4 \uc26c\uc6b4 \uacbd\uc6b0\ub85c, \ud45c\ud604 \ubc94\uc704\uac00 \ud070 \ud0c0\uc785\uc5d0\uc11c \uc791\uc740 \ud0c0\uc785\uc73c\ub85c \ubcc0\ud658 \ub420 \ub54c \uac12\uc744 \uc783\uc5b4 \ubc84\ub824\uc11c \uc6d0\ud558\uc9c0 \uc54a\ub294 \uacb0\uacfc\uac00 \uc0dd\uae38 \uc218\ub3c4 \uc788\ub294\ub370, \uc774 \uacbd\uc6b0\ub294 -Wconversion switch\ub97c \ucd94\uac00\ud558\uba74 \ucef4\ud30c\uc77c\uc2dc\uac04\uc5d0 \uc7a1\uc544\ub0b4\uc11c \uacbd\uace0\ub97c \ucd9c\ub825\ud558\ub3c4\ub85d \ud560 \uc218 \uc788\ub2e4. \uc608\ub97c \ub4e4\uc5b4 64bit \uc2dc\uc2a4\ud15c\uc5d0\uc11c unsigned long type\uc778 size_t\ub97c \uc2e4\uc218\ub85c unsigned int\uc5d0 \ud560\ub2f9\ud55c \uac83\uacfc \uac19\uc740 \uacbd\uc6b0\ub4e4\uc744 \ucef4\ud30c\uc77c \uc2dc\uac04\uc5d0 \ucc3e\uc544 \uacbd\uace0\ub97c \ucd9c\ub825\ud574 \uc8fc\ub294\ub370 -Weror\uc640 \ud568\uaed8 \uc0ac\uc6a9\ud558\uba74 \ucef4\ud30c\uc77c\uc774 \uba48\ucd94\uac8c \ub41c\ub2e4.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\uacb0\ub860<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\ucf54\ub529\uc758 \ucc98\uc74c\ubd80\ud130 \uc548\uc804\ud55c \uc5f0\uc0b0\uc744 \uace0\ub824 \ud55c\ub2e4\uba74 \uc774\ub97c \uc9c0\uc6d0\ud558\uae30 \uc704\ud55c \ub77c\uc774\ube0c\ub7ec\ub9ac\ub4e4\uc744 \uace0\ub824\ud574 \ubcfc \uc218 \uc788\uaca0\uc9c0\ub9cc, \ucef4\ud30c\uc77c\ub7ec \uc2a4\uc704\uce58\ub97c \ud65c\uc6a9\ud558\uc5ec arithmetic integer overflow \ubc1c\uc0dd\uc5d0 \ub300\ud55c \ub300\ube44\ub97c \ud560 \uc218\ub3c4 \uc788\ub2e4.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">* \uc704\uc758 \uc608\uc81c\ub4e4\uc740 Ubuntu 18.04\uc5d0\uc11c g++ 7.5.0\uc73c\ub85c \uc2dc\ud5d8 \ub418\uc5c8\ub2e4.<br>** \uc704\uc758 fwrapv \uc608\uc81c\uc5d0 -fwrapv\uc640 -ftrapv switch\ub97c \ubaa8\ub450 \uc0ac\uc6a9\ud558\uba74 -fwrapv\ub85c \ub3d9\uc791\ud55c\ub2e4.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Arithmetic overflow\ub294 \ubd80\ud638 \uc788\ub294 \ubcc0\uc218(signed variable)\uac00 \ud45c\uc2dc \ud560 \uc218 \uc788\ub294 \ucd5c\ub313\uac12 \/ \ucd5c\uc19f\uac12\uc744 \ub118\uc5b4 \uc130\uc744 \ub54c \ubd80\ud638\uac00 \ubc14\ub00c\uba74\uc11c \uc6d0\ud558\uc9c0 \uc54a\ub294 \uacb0\uacfc\uac00 \ub098\ud0c0\ub098\ub294 \uacbd\uc6b0\ub97c \ub9d0\ud55c\ub2e4. \uc704\uc758 \ucf54\ub4dc\ub97c \ub2e4\uc74c\uacfc \uac19\uc774 \ucef4\ud30c\uc77c\ud558\uace0 \uc2e4\ud589\ud558\uba74 overflow\uac00 \ubc1c\uc0dd\ud55c\ub2e4. \uc774\uc640 \uac19\uc740 \uacbd\uc6b0\ub97c \ubc29\uc9c0 \ud558\ub824\uba74 \ubb3c\ub860 \uaf3c\uaf3c\ud55c \ucf54\ub4dc \ub9ac\ubdf0\ub3c4 \uc911\uc694 \ud558\uc9c0\uaca0\ub9cc \ucef4\ud30c\uc77c\ub7ec\uc5d0\uc11c \uc81c\uacf5\ud558\ub294 overflow\ub97c \uc810\uac80\ud558\ub294 \ube4c\ud2b8\uc778 \ud568\uc218\ub97c \uc0ac\uc6a9\ud558\uac70\ub098 Safeint \ud639\uc740 \uc774\uc640 \uc720\uc0ac\ud55c Boost\uc758 [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[250,247,256,255,254,253,252,251],"class_list":["post-2627","post","type-post","status-publish","format-standard","hentry","category-linux","tag-arithmetic-overflow","tag-c","tag-g","tag-gcc","tag-overflow","tag-safe-numerics","tag-safeint","tag-signed-integer"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/litcoder.com\/index.php?rest_route=\/wp\/v2\/posts\/2627","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/litcoder.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/litcoder.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/litcoder.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/litcoder.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2627"}],"version-history":[{"count":24,"href":"https:\/\/litcoder.com\/index.php?rest_route=\/wp\/v2\/posts\/2627\/revisions"}],"predecessor-version":[{"id":2693,"href":"https:\/\/litcoder.com\/index.php?rest_route=\/wp\/v2\/posts\/2627\/revisions\/2693"}],"wp:attachment":[{"href":"https:\/\/litcoder.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2627"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/litcoder.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2627"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/litcoder.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2627"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}