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浼熷ぇ鐨凚ill Gates 鏇劇粡澶辮█錛?br>
銆銆640K ought to be enough for everybody 鈥?Bill Gates 1981
銆銆紼嬪簭鍛樹滑緇忓父緙栧啓鍐呭瓨綆$悊紼嬪簭錛屽線寰鎻愬績鍚婅儐銆傚鏋滀笉鎯寵Е闆鳳紝鍞竴鐨勮В鍐沖姙娉曞氨鏄彂鐜版墍鏈夋綔浼忕殑鍦伴浄騫朵笖鎺掗櫎瀹冧滑錛岃翰鏄翰涓嶄簡鐨勩傛湰鏂囩殑鍐呭姣斾竴鑸暀縐戜功鐨勮娣卞叆寰楀錛岃鑰呴渶緇嗗績闃呰錛屽仛鍒扮湡姝e湴閫氭檽鍐呭瓨綆$悊銆?br>
銆銆1銆佸唴瀛樺垎閰嶆柟寮?/strong>
銆銆鍐呭瓨鍒嗛厤鏂瑰紡鏈変笁縐嶏細
銆銆錛?錛変粠闈欐佸瓨鍌ㄥ尯鍩熷垎閰嶃傚唴瀛樺湪紼嬪簭緙栬瘧鐨勬椂鍊欏氨宸茬粡鍒嗛厤濂斤紝榪欏潡鍐呭瓨鍦ㄧ▼搴忕殑鏁翠釜榪愯鏈熼棿閮藉瓨鍦ㄣ備緥濡傚叏灞鍙橀噺錛宻tatic鍙橀噺銆?br>
銆銆錛?錛夊湪鏍堜笂鍒涘緩銆傚湪鎵ц鍑芥暟鏃訛紝鍑芥暟鍐呭眬閮ㄥ彉閲忕殑瀛樺偍鍗曞厓閮藉彲浠ュ湪鏍堜笂鍒涘緩錛屽嚱鏁版墽琛岀粨鏉熸椂榪欎簺瀛樺偍鍗曞厓鑷姩琚噴鏀俱傛爤鍐呭瓨鍒嗛厤榪愮畻鍐呯疆浜庡鐞嗗櫒鐨勬寚浠ら泦涓紝鏁堢巼寰堥珮錛屼絾鏄垎閰嶇殑鍐呭瓨瀹歸噺鏈夐檺銆?br>
銆銆錛?錛?浠庡爢涓婂垎閰嶏紝浜︾О鍔ㄦ佸唴瀛樺垎閰嶃傜▼搴忓湪榪愯鐨勬椂鍊欑敤malloc鎴杗ew鐢寵浠繪剰澶氬皯鐨勫唴瀛橈紝紼嬪簭鍛樿嚜宸辮礋璐e湪浣曟椂鐢╢ree鎴杁elete閲婃斁鍐呭瓨銆傚姩鎬佸唴瀛樼殑鐢熷瓨鏈熺敱鎴戜滑鍐沖畾錛屼嬌鐢ㄩ潪甯哥伒媧伙紝浣嗛棶棰樹篃鏈澶氥?br>
銆銆2銆佸父瑙佺殑鍐呭瓨閿欒鍙婂叾瀵圭瓥
銆銆鍙戠敓鍐呭瓨閿欒鏄歡闈炲父楹葷儲鐨勪簨鎯呫傜紪璇戝櫒涓嶈兘鑷姩鍙戠幇榪欎簺閿欒錛岄氬父鏄湪紼嬪簭榪愯鏃舵墠鑳芥崟鎹夊埌銆傝岃繖浜涢敊璇ぇ澶氭病鏈夋槑鏄劇殑鐥囩姸錛屾椂闅愭椂鐜幫紝澧炲姞浜嗘敼閿欑殑闅懼害銆傛湁鏃剁敤鎴鋒掓皵鍐插啿鍦版妸浣犳壘鏉ワ紝紼嬪簭鍗存病鏈夊彂鐢熶換浣曢棶棰橈紝浣犱竴璧幫紝閿欒鍙堝彂浣滀簡銆?甯歌鐨勫唴瀛橀敊璇強鍏跺絳栧涓嬶細
銆銆* 鍐呭瓨鍒嗛厤鏈垚鍔燂紝鍗翠嬌鐢ㄤ簡瀹冦?br>
銆銆緙栫▼鏂版墜甯哥姱榪欑閿欒錛屽洜涓轟粬浠病鏈夋剰璇嗗埌鍐呭瓨鍒嗛厤浼氫笉鎴愬姛銆傚父鐢ㄨВ鍐沖姙娉曟槸錛屽湪浣跨敤鍐呭瓨涔嬪墠媯鏌ユ寚閽堟槸鍚︿負NULL銆傚鏋滄寚閽坧鏄嚱鏁扮殑鍙傛暟錛岄偅涔堝湪鍑芥暟鐨勫叆鍙e鐢╝ssert(p!=NULL)榪涜
銆銆媯鏌ャ傚鏋滄槸鐢╩alloc鎴杗ew鏉ョ敵璇峰唴瀛橈紝搴旇鐢╥f(p==NULL) 鎴杋f(p!=NULL)榪涜闃查敊澶勭悊銆?br>
銆銆* 鍐呭瓨鍒嗛厤铏界劧鎴愬姛錛屼絾鏄皻鏈垵濮嬪寲灝卞紩鐢ㄥ畠銆?br>
鐘繖縐嶉敊璇富瑕佹湁涓や釜璧峰洜錛氫竴鏄病鏈夊垵濮嬪寲鐨勮蹇碉紱浜屾槸璇互涓哄唴瀛樼殑緙虹渷鍒濆煎叏涓洪浂錛屽鑷村紩鐢ㄥ垵鍊奸敊璇紙渚嬪鏁扮粍錛夈?
鍐呭瓨鐨勭己鐪佸垵鍊肩┒绔熸槸浠涔堝茍娌℃湁緇熶竴鐨勬爣鍑嗭紝灝界鏈変簺鏃跺欎負闆跺鹼紝鎴戜滑瀹佸彲淇″叾鏃犱笉鍙俊鍏舵湁銆傛墍浠ユ棤璁虹敤浣曠鏂瑰紡鍒涘緩鏁扮粍錛岄兘鍒繕浜嗚祴鍒濆鹼紝鍗充究鏄祴闆跺?
涔熶笉鍙渷鐣ワ紝涓嶈瀚岄夯鐑︺?br>
銆銆* 鍐呭瓨鍒嗛厤鎴愬姛騫朵笖宸茬粡鍒濆鍖栵紝浣嗘搷浣滆秺榪囦簡鍐呭瓨鐨勮竟鐣屻?br>
銆銆渚嬪鍦ㄤ嬌鐢ㄦ暟緇勬椂緇忓父鍙戠敓涓嬫爣“澶?”鎴栬?#8220;灝?”鐨勬搷浣溿傜壒鍒槸鍦╢or寰幆璇彞涓紝寰幆嬈℃暟寰堝鏄撴悶閿欙紝瀵艱嚧鏁扮粍鎿嶄綔瓚婄晫銆?br>
銆銆* 蹇樿浜嗛噴鏀懼唴瀛橈紝閫犳垚鍐呭瓨娉勯湶銆?br>
銆銆鍚湁榪欑閿欒鐨勫嚱鏁版瘡琚皟鐢ㄤ竴嬈″氨涓㈠け涓鍧楀唴瀛樸傚垰寮濮嬫椂緋葷粺鐨勫唴瀛樺厖瓚籌紝浣犵湅涓嶅埌閿欒銆傜粓鏈変竴嬈$▼搴忕獊鐒舵鎺夛紝緋葷粺鍑虹幇鎻愮ず錛氬唴瀛樿楀敖銆?br>
銆銆鍔ㄦ佸唴瀛樼殑鐢寵涓庨噴鏀懼繀欏婚厤瀵癸紝紼嬪簭涓璵alloc涓巉ree鐨勪嬌鐢ㄦ鏁頒竴瀹氳鐩稿悓錛屽惁鍒欒偗瀹氭湁閿欒錛坣ew/delete鍚岀悊錛夈?br>
銆銆* 閲婃斁浜嗗唴瀛樺嵈緇х畫浣跨敤瀹冦?br>銆
銆銆鏈変笁縐嶆儏鍐碉細
銆銆錛?錛夌▼搴忎腑鐨勫璞¤皟鐢ㄥ叧緋昏繃浜庡鏉傦紝瀹炲湪闅句互鎼炴竻妤氭煇涓璞$┒绔熸槸鍚﹀凡緇忛噴鏀句簡鍐呭瓨錛屾鏃跺簲璇ラ噸鏂拌璁℃暟鎹粨鏋勶紝浠庢牴鏈笂瑙e喅瀵硅薄綆$悊鐨勬販涔卞眬闈€?br>
銆銆錛?錛夊嚱鏁扮殑return璇彞鍐欓敊浜嗭紝娉ㄦ剰涓嶈榪斿洖鎸囧悜“鏍堝唴瀛?#8221;鐨?#8220;鎸囬拡”鎴栬?#8220;寮曠敤”錛屽洜涓鴻鍐呭瓨鍦ㄥ嚱鏁頒綋緇撴潫鏃惰鑷姩閿姣併?br>
銆銆錛?錛変嬌鐢╢ree鎴杁elete閲婃斁浜嗗唴瀛樺悗錛屾病鏈夊皢鎸囬拡璁劇疆涓篘ULL銆傚鑷翠駭鐢?#8220;閲庢寚閽?#8221;銆?br>
銆銆銆愯鍒?銆戠敤malloc鎴杗ew鐢寵鍐呭瓨涔嬪悗錛屽簲璇ョ珛鍗蟲鏌ユ寚閽堝兼槸鍚︿負NULL銆傞槻姝嬌鐢ㄦ寚閽堝間負NULL鐨勫唴瀛樸?br>
銆銆銆愯鍒?銆戜笉瑕佸繕璁頒負鏁扮粍鍜屽姩鎬佸唴瀛樿祴鍒濆箋傞槻姝㈠皢鏈鍒濆鍖栫殑鍐呭瓨浣滀負鍙沖間嬌鐢ㄣ?br>
銆銆銆愯鍒?銆戦伩鍏嶆暟緇勬垨鎸囬拡鐨勪笅鏍囪秺鐣岋紝鐗瑰埆瑕佸綋蹇冨彂鐢?#8220;澶?”鎴栬?#8220;灝?”鎿嶄綔銆?br>
銆銆銆愯鍒?銆戝姩鎬佸唴瀛樼殑鐢寵涓庨噴鏀懼繀欏婚厤瀵癸紝闃叉鍐呭瓨娉勬紡銆?br>
銆銆銆愯鍒?銆戠敤free鎴杁elete閲婃斁浜嗗唴瀛樹箣鍚庯紝绔嬪嵆灝嗘寚閽堣緗負NULL錛岄槻姝駭鐢?#8220;閲庢寚閽?#8221;銆?br>
銆銆3銆佹寚閽堜笌鏁扮粍鐨勫姣?/strong>
銆銆C++/C紼嬪簭涓紝鎸囬拡鍜屾暟緇勫湪涓嶅皯鍦版柟鍙互鐩鎬簰鏇挎崲鐫鐢紝璁╀漢浜х敓涓縐嶉敊瑙夛紝浠ヤ負涓よ呮槸絳変環鐨勩?br>
銆銆鏁扮粍瑕佷箞鍦ㄩ潤鎬佸瓨鍌ㄥ尯琚垱寤猴紙濡傚叏灞鏁扮粍錛夛紝瑕佷箞鍦ㄦ爤涓婅鍒涘緩銆傛暟緇勫悕瀵瑰簲鐫錛堣屼笉鏄寚鍚戯級涓鍧楀唴瀛橈紝鍏跺湴鍧涓庡閲忓湪鐢熷懡鏈熷唴淇濇寔涓嶅彉錛屽彧鏈夋暟緇勭殑鍐呭鍙互鏀瑰彉銆?br>
銆銆鎸囬拡鍙互闅忔椂鎸囧悜浠繪剰綾誨瀷鐨勫唴瀛樺潡錛屽畠鐨勭壒寰佹槸“鍙彉”錛屾墍浠ユ垜浠父鐢ㄦ寚閽堟潵鎿嶄綔鍔ㄦ佸唴瀛樸傛寚閽堣繙姣旀暟緇勭伒媧伙紝浣嗕篃鏇村嵄闄┿?br>
銆銆涓嬮潰浠ュ瓧絎︿覆涓轟緥姣旇緝鎸囬拡涓庢暟緇勭殑鐗規с?br>
銆銆3.1 淇敼鍐呭
紺轟緥3-1涓紝瀛楃鏁扮粍a鐨勫閲忔槸6涓瓧絎︼紝鍏跺唴瀹逛負hello銆俛鐨勫唴瀹瑰彲浠ユ敼鍙橈紝濡俛[0]=
‘X’銆傛寚閽坧鎸囧悜甯擱噺瀛楃涓?#8220;world”錛堜綅浜庨潤鎬佸瓨鍌ㄥ尯錛屽唴瀹逛負world錛夛紝甯擱噺瀛楃涓茬殑鍐呭鏄笉鍙互琚慨鏀圭殑銆備粠璇硶涓婄湅錛岀紪璇戝櫒騫朵笉瑙夊緱璇彞
p[0]= ‘X’鏈変粈涔堜笉濡ワ紝浣嗘槸璇ヨ鍙ヤ紒鍥句慨鏀瑰父閲忓瓧絎︿覆鐨勫唴瀹硅屽鑷磋繍琛岄敊璇?br>
char a[] = “hello”; a[0] = ‘X’; cout << a << endl; char *p = “world”; // 娉ㄦ剰p鎸囧悜甯擱噺瀛楃涓?br>p[0] = ‘X’; // 緙栬瘧鍣ㄤ笉鑳藉彂鐜拌閿欒 cout << p << endl; |
// 鏁扮粍… char a[] = "hello"; char b[10]; strcpy(b, a); // 涓嶈兘鐢?b = a; if(strcmp(b, a) == 0) // 涓嶈兘鐢?if (b == a) … // 鎸囬拡… int len = strlen(a); char *p = (char *)malloc(sizeof(char)*(len+1)); strcpy(p,a); // 涓嶈鐢?p = a; if(strcmp(p, a) == 0) // 涓嶈鐢?if (p == a) … |
char a[] = "hello world"; char *p = a; cout<< sizeof(a) << endl; // 12瀛楄妭 cout<< sizeof(p) << endl; // 4瀛楄妭 |
void Func(char a[100]) { 銆cout<< sizeof(a) << endl; // 4瀛楄妭鑰屼笉鏄?00瀛楄妭 } |
銆銆銆銆銆紺轟緥3.3錛坆錛?鏁扮粍閫鍖栦負鎸囬拡
銆銆4銆佹寚閽堝弬鏁版槸濡備綍浼犻掑唴瀛樼殑錛?br>
銆銆濡傛灉鍑芥暟鐨勫弬鏁版槸涓涓寚閽堬紝涓嶈鎸囨湜鐢ㄨ鎸囬拡鍘葷敵璇峰姩鎬佸唴瀛樸傜ず渚?-4-1涓紝Test鍑芥暟鐨勮鍙etMemory(str, 200)騫舵病鏈変嬌str鑾峰緱鏈熸湜鐨勫唴瀛橈紝str渚濇棫鏄疦ULL錛屼負浠涔堬紵
void GetMemory(char *p, int num) { 銆p = (char *)malloc(sizeof(char) * num); } void Test(void) { 銆char *str = NULL; 銆GetMemory(str, 100); // str 浠嶇劧涓?NULL 銆strcpy(str, "hello"); // 榪愯閿欒 } |
void GetMemory2(char **p, int num) { 銆*p = (char *)malloc(sizeof(char) * num); } void Test2(void) { 銆char *str = NULL; 銆GetMemory2(&str, 100); // 娉ㄦ剰鍙傛暟鏄?&str錛岃屼笉鏄痵tr 銆strcpy(str, "hello"); 銆cout<< str << endl; 銆free(str); } |
char *GetMemory3(int num) { 銆char *p = (char *)malloc(sizeof(char) * num); 銆return p; } void Test3(void) { 銆char *str = NULL; 銆str = GetMemory3(100); 銆strcpy(str, "hello"); 銆cout<< str << endl; 銆free(str); } |
char *GetString(void) { 銆char p[] = "hello world"; 銆return p; // 緙栬瘧鍣ㄥ皢鎻愬嚭璀﹀憡 } void Test4(void) { 銆char *str = NULL; 銆str = GetString(); // str 鐨勫唴瀹規槸鍨冨溇 銆cout<< str << endl; } |
char *GetString2(void) { 銆char *p = "hello world"; 銆return p; } void Test5(void) { 銆char *str = NULL; 銆str = GetString2(); 銆cout<< str << endl; } |
char *p = NULL; char *str = (char *) malloc(100); |
class A { 銆public: 銆銆void Func(void){ cout << “Func of class A” << endl; } }; void Test(void) { 銆A *p; 銆{ 銆銆A a; 銆銆p = &a; // 娉ㄦ剰 a 鐨勭敓鍛芥湡 銆} 銆p->Func(); // p鏄?#8220;閲庢寚閽?#8221; } |
銆銆鍑芥暟Test鍦ㄦ墽琛岃鍙->Func()鏃訛紝瀵硅薄a宸茬粡娑堝け錛岃宲鏄寚鍚慳鐨勶紝鎵浠灝辨垚浜?#8220;閲庢寚閽?#8221;銆備絾濂囨殑鏄垜榪愯榪欎釜紼嬪簭鏃跺眳鐒舵病鏈夊嚭閿欙紝榪欏彲鑳戒笌緙栬瘧鍣ㄦ湁鍏熾?/p>
銆銆6銆佹湁浜唌alloc/free涓轟粈涔堣繕瑕乶ew/delete錛?br>
銆銆malloc涓巉ree鏄疌++/C璇█鐨勬爣鍑嗗簱鍑芥暟錛宯ew/delete鏄疌++鐨勮繍綆楃銆傚畠浠兘鍙敤浜庣敵璇峰姩鎬佸唴瀛樺拰閲婃斁鍐呭瓨銆?br>
瀵逛簬闈炲唴閮ㄦ暟鎹被鍨嬬殑瀵硅薄鑰岃█錛屽厜鐢╩aloc/free鏃犳硶婊¤凍鍔ㄦ佸璞$殑瑕佹眰銆傚璞″湪鍒涘緩鐨勫悓鏃惰鑷姩鎵ц鏋勯犲嚱鏁幫紝瀵硅薄鍦ㄦ秷浜′箣鍓嶈鑷姩鎵ц鏋愭瀯
鍑芥暟銆傜敱浜巑alloc/free鏄簱鍑芥暟鑰屼笉鏄繍綆楃錛屼笉鍦ㄧ紪璇戝櫒鎺у埗鏉冮檺涔嬪唴錛屼笉鑳藉鎶婃墽琛屾瀯閫犲嚱鏁板拰鏋愭瀯鍑芥暟鐨勪換鍔″己鍔犱簬malloc/free銆?br>
鍥犳C++璇█闇瑕佷竴涓兘瀹屾垚鍔ㄦ佸唴瀛樺垎閰嶅拰鍒濆鍖栧伐浣滅殑榪愮畻絎ew錛屼互鍙婁竴涓兘瀹屾垚娓呯悊涓庨噴鏀懼唴瀛樺伐浣滅殑榪愮畻絎elete銆傛敞鎰?
new/delete涓嶆槸搴撳嚱鏁般傛垜浠厛鐪嬩竴鐪媘alloc/free鍜宯ew/delete濡備綍瀹炵幇瀵硅薄鐨勫姩鎬佸唴瀛樼鐞嗭紝瑙佺ず渚?銆?br>
class Obj { 銆public : 銆銆Obj(void){ cout << “Initialization” << endl; } 銆銆~Obj(void){ cout << “Destroy” << endl; } 銆銆void Initialize(void){ cout << “Initialization” << endl; } 銆銆void Destroy(void){ cout << “Destroy” << endl; } }; void UseMallocFree(void) { 銆Obj *a = (obj *)malloc(sizeof(obj)); // 鐢寵鍔ㄦ佸唴瀛?br>銆a->Initialize(); // 鍒濆鍖?br>銆//… 銆a->Destroy(); // 娓呴櫎宸ヤ綔 銆free(a); // 閲婃斁鍐呭瓨 } void UseNewDelete(void) { 銆Obj *a = new Obj; // 鐢寵鍔ㄦ佸唴瀛樺茍涓斿垵濮嬪寲 銆//… 銆delete a; // 娓呴櫎騫朵笖閲婃斁鍐呭瓨 } |
void Func(void) { 銆A *a = new A; 銆if(a == NULL) 銆{ 銆銆return; 銆} 銆… } |
void Func(void) { 銆A *a = new A; 銆if(a == NULL) 銆{ 銆銆cout << “Memory Exhausted” << endl; 銆銆exit(1); 銆} 銆… } |
void main(void) { 銆float *p = NULL; 銆while(TRUE) 銆{ 銆銆p = new float[1000000]; 銆銆cout << “eat memory” << endl; 銆銆if(p==NULL) 銆銆銆exit(1); 銆} } |
銆銆紺轟緥7璇曞浘鑰楀敖鎿嶄綔緋葷粺鐨勫唴瀛?/p>
銆銆8銆乵alloc/free 鐨勪嬌鐢ㄨ鐐?br>
銆銆鍑芥暟malloc鐨勫師鍨嬪涓嬶細
void * malloc(size_t size); |
int *p = (int *) malloc(sizeof(int) * length); |
cout << sizeof(char) << endl; cout << sizeof(int) << endl; cout << sizeof(unsigned int) << endl; cout << sizeof(long) << endl; cout << sizeof(unsigned long) << endl; cout << sizeof(float) << endl; cout << sizeof(double) << endl; cout << sizeof(void *) << endl; |
void free( void * memblock ); |
int *p1 = (int *)malloc(sizeof(int) * length); int *p2 = new int[length]; |
class Obj { 銆public : 銆銆Obj(void); // 鏃犲弬鏁扮殑鏋勯犲嚱鏁?br>銆銆Obj(int x); // 甯︿竴涓弬鏁扮殑鏋勯犲嚱鏁?br>銆銆… } void Test(void) { 銆Obj *a = new Obj; 銆Obj *b = new Obj(1); // 鍒濆間負1 銆… 銆delete a; 銆delete b; } |
Obj *objects = new Obj[100]; // 鍒涘緩100涓姩鎬佸璞?/td> |
Obj *objects = new Obj[100](1);// 鍒涘緩100涓姩鎬佸璞$殑鍚屾椂璧嬪垵鍊? |
delete []objects; // 姝g‘鐨勭敤娉?br>delete objects; // 閿欒鐨勭敤娉?/td> |