{"id":1210,"date":"2018-12-05T20:02:43","date_gmt":"2018-12-05T18:02:43","guid":{"rendered":"http:\/\/www.fabienm.eu\/wordpress\/?p=1210"},"modified":"2018-12-06T23:04:22","modified_gmt":"2018-12-06T21:04:22","slug":"bug-c-du-jour","status":"publish","type":"post","link":"http:\/\/www.fabienm.eu\/wordpress\/2018\/12\/05\/bug-c-du-jour\/","title":{"rendered":"Bug C du jour"},"content":{"rendered":"

Qu’affiche le code suivant ?<\/p>\n

char* states[] = {\r\n    \"PLOP\",\r\n    \"PLIP\",\r\n    \"BOUHHH\",\r\n    \"CROTTE\",\r\n    \"DINGDING\",\r\n    \"CAFE\",\r\n    \"UB40\"\r\n    \"GWB\",\r\n};\r\nchar * others_string[] = {\r\n    \"ROGER\",\r\n    \"RABBIT\",\r\n};\r\n[...]\r\n\r\nprintf(\"State %s\\n\", states[7]);\r\n<\/pre>\n
Je pr\u00e9cise que je compile toujours en -Wall et que je n’avais aucun warning bien s\u00fbr !<\/p>\n
[edit 6 d\u00e9cembre 2018]<\/p>\n
Si c’est un compilateur GCC pour ARM sur APF6<\/a> (j’ai pas toutes les options en t\u00eate) la fonction printf affiche :<\/p>\n
State ROGER\r\n<\/pre>\n
Par contre sur un pc (debian) sans aucune option sp\u00e9cifique :<\/p>\n
State (null)\r\n<\/pre>\n
Et oui \u00e7a n’est pas vu comme un bug … puisque \u00e7a compile en -Wall et que \u00e7a s’ex\u00e9cute sans probl\u00e8me (enfin pour l’ex\u00e9cution il y a quand m\u00eame une histoire de pointeur qui va trifouiller au mauvais endroit de la m\u00e9moire sur la version \u00abembarqu\u00e9es\u00bb).<\/p>\n
Tout simplement car deux cha\u00eenes de caract\u00e8res c\u00f4tes \u00e0 c\u00f4tes sont consid\u00e9r\u00e9es comme une seule et m\u00eame cha\u00eene.
\nIci \u00ab\u00a0UB40\u00a0\u00bb et \u00ab\u00a0GWB\u00a0\u00bb ne sont pas deux cha\u00eenes de caract\u00e8res distinctes mais une seule et m\u00eame cha\u00eene : \u00ab\u00a0UB40GWB\u00a0\u00bb. Il n’y a pas d’index num\u00e9ro 7 et donc on d\u00e9borde sur la suite … qui est \u00e9galement un tableau de pointeurs sur cha\u00eenes de caract\u00e8res. Du coup \u00e7a ne le d\u00e9range pas de l’afficher.
\ncqfd<\/p>\n","protected":false},"excerpt":{"rendered":"
Qu’affiche le code suivant ? char* states[] = { \u00ab\u00a0PLOP\u00a0\u00bb, \u00ab\u00a0PLIP\u00a0\u00bb, \u00ab\u00a0BOUHHH\u00a0\u00bb, \u00ab\u00a0CROTTE\u00a0\u00bb, \u00ab\u00a0DINGDING\u00a0\u00bb, \u00ab\u00a0CAFE\u00a0\u00bb, \u00ab\u00a0UB40\u00a0\u00bb \u00ab\u00a0GWB\u00a0\u00bb, }; char * others_string[] = { \u00ab\u00a0ROGER\u00a0\u00bb, \u00ab\u00a0RABBIT\u00a0\u00bb, }; […] printf(\u00ab\u00a0State %s\\n\u00a0\u00bb, states[7]); Je pr\u00e9cise que je compile toujours en -Wall et que … Continuer la lecture →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"aside","meta":{"footnotes":""},"categories":[10,11],"tags":[202,58,143],"class_list":["post-1210","post","type-post","status-publish","format-aside","hentry","category-informatique","category-programmation","tag-bug","tag-c","tag-programmation","post_format-post-format-aside"],"_links":{"self":[{"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts\/1210","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/comments?post=1210"}],"version-history":[{"count":5,"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts\/1210\/revisions"}],"predecessor-version":[{"id":1217,"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts\/1210\/revisions\/1217"}],"wp:attachment":[{"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/media?parent=1210"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/categories?post=1210"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/tags?post=1210"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}