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Algorithms Algorithms(算法) bsearch bsearch_s qsort qsort_s Atomic operations Atomic operations library(原子操作庫) ATOMIC_*_LOCK_FREE atomic_compare_exchange_strong atomic_compare_exchange_strong_explicit atomic_compare_exchange_weak atomic_compare_exchange_weak_explicit atomic_exchange atomic_exchange_explicit atomic_fetch_add atomic_fetch_add_explicit atomic_fetch_and atomic_fetch_and_explicit atomic_fetch_or atomic_fetch_or_explicit atomic_fetch_sub atomic_fetch_sub_explicit atomic_fetch_xor atomic_fetch_xor_explicit atomic_flag atomic_flag_clear atomic_flag_clear_explicit ATOMIC_FLAG_INIT atomic_flag_test_and_set atomic_flag_test_and_set_explicit atomic_init atomic_is_lock_free atomic_load atomic_load_explicit atomic_signal_fence atomic_store atomic_store_explicit atomic_thread_fence(線程圍欄) ATOMIC_VAR_INIT kill_dependency memory_order(內(nèi)存排序) C keywords auto(自動存儲) break(跳出循環(huán)) C keywords(關(guān)鍵詞) case char const(常量修飾符) continue default(預(yù)設(shè)運(yùn)算式) do double(雙精度浮點(diǎn)型) else enum(枚舉類型) extern(全局變量) float(浮點(diǎn)數(shù)) for fortran goto(goto語句) if(if語句) inline(行內(nèi)函式) int long(長整型) register(寄存器變量) restrict( restrict類型限定符) return short signed sizeof(sizeof運(yùn)算符) static(靜態(tài)變量) struct(結(jié)構(gòu)體) switch(switch語句) typedef(typedef關(guān)鍵字) union(聯(lián)合體) unsigned(無符號) void(空類型) volatile(volatile變量) while(while語句) _Alignas _Alignof _Atomic _Bool _Complex _Generic _Imaginary _Noreturn _Static_assert _Thread_local C language #define directive #elif directive #else directive #endif directive #error directive #if directive #ifdef directive #ifndef directive #include directive #line directive #pragma directive alignas(對齊指定符) Alternative operators and tokens(替代運(yùn)算符和令牌) Analyzability Arithmetic operators Arithmetic types Array declaration(數(shù)組聲明) Array initialization(陣列初始化) ASCII Chart Assignment operators(賦值運(yùn)算符) types(atomic類型限定符) Basic concepts Bit fields(位域) break statement C language C Operator Precedence cast operator character constant(字符字面量) Comments(注釋符) Comparison operators(比較運(yùn)算符) compound literals(符合字面量) Conditional inclusion(條件包含) Conformance(一致性) const type qualifier(const 限定符) Constant expressions(常量表達(dá)) continue statement Declarations(聲明) do-while loop Enumerations(枚舉類型) Escape sequences(轉(zhuǎn)義字符) Expressions(表達(dá)式) External and tentative definitions(外部和暫定的定義) File scope(文件范圍) floating constant(浮點(diǎn)常量) for loop Function declarations(函數(shù)聲明) Function definitions(函數(shù)聲明) Functions Generic selection泛型選擇 goto statement Identifier(標(biāo)示符) if statement Implicit conversions(隱式轉(zhuǎn)換) Increment/decrement operators(前置/后置操作符) Initialization(初始化) inline function specifier(內(nèi)聯(lián)函式) integer constant Lifetime(生命期) Logical operators(邏輯運(yùn)算符) Lookup and name spaces Main function(主函式) Member access operators(會員接入運(yùn)營商) Memory model Objects and alignment(字節(jié)對齊) Order of evaluation(評估順序) Other operators Phases of translation(翻譯階段) Pointer declaration Preprocessor(預(yù)處理) restrict type qualifier(restrict類型限定符) return statement Scalar initialization(標(biāo)量類型初始化) Scope(范圍) sizeof operator(sizeof運(yùn)算符) Statements(陳述) static assert declaration(靜態(tài)斷言聲明) Static storage duration(靜態(tài)存儲周期) Storage-class specifiers(存儲類說明符) string literals(字符串字面量) Struct and union initialization(結(jié)構(gòu)體與聯(lián)合體初始化) Struct declaration(結(jié)構(gòu)體聲明) switch statement Thread storage duration(線程存儲時間) Type Type(類型) Typedef declaration(Typedef聲明) Undefined behavior(未定義行為) Union declaration(聯(lián)合體聲明) Value categories(值類別) Variadic arguments(變長參數(shù)宏) volatile type qualifier(volatile 類型限定符) while loop _Alignof operator _Noreturn function specifier Date and time asctime(asctime函數(shù)) asctime_s clock CLOCKS_PER_SEC clock_t ctime(ctime函數(shù)) ctime_s Date and time utilities(日期和時間庫) difftime(計算兩個時間的間隔) gmtime gmtime_s localtime localtime_s mktime(將時間結(jié)構(gòu)數(shù)據(jù)轉(zhuǎn)換成經(jīng)過的秒數(shù)的函數(shù)) strftime(格式化輸出時間函數(shù)) time timespec timespec_get time_t tm wcsftime(格式化時間寬字符) Dynamic memory management aligned_alloc C memory management library(內(nèi)存管理庫) calloc free(釋放動態(tài)分配空間的函數(shù)) malloc(動態(tài)分配內(nèi)存空間的函數(shù)) realloc(重新分配內(nèi)存空間的函數(shù)) Error handling abort_handler_s assert(斷言) constraint_handler_t errno(錯誤報告) Error handling(錯誤處理) Error numbers(錯誤個數(shù)) ignore_handler_s set_constraint_handler_s static_assert File input/output clearerr(清除/復(fù)位) fclose feof ferror fflush(清空文件緩沖區(qū)) fgetc fgetpos fgets fgetwc fgetws File input/output fopen fopen_s fprintf fprintf_s fputc fputs fputwc fputws fread freopen freopen_s fscanf fscanf_s fseek fsetpos ftell fwide fwprintf fwprintf_s fwrite fwscanf fwscanf_s getc getchar gets gets_s getwchar perror printf printf_s putc putchar puts putwc putwchar remove rename rewind scanf scanf_s setbuf setvbuf snprintf sprintf sscanf sscanf_s swprintf swprintf_s swscanf swscanf_s tmpfile tmpfile_s tmpnam tmpnam_s ungetc ungetwc vfprintf vfprintf_s vfscanf vfscanf_s vfwprintf vfwprintf_s vfwscanf vfwscanf_s vprintf vprintf_s vscanf vscanf_s vsnprintf vsprintf vsscanf vsscanf_s vswprintf vswprintf_s vswscanf vswscanf_s vwprintf vwprintf_s vwscanf vwscanf_s wprintf wprintf_s wscanf wscanf_s Localization support lconv LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME localeconv Localization support setlocale Numerics abs acos acosf acosh acoshf acoshl acosl asin asinf asinh asinhf asinhl asinl atan atan2 atan2f atan2l atanf atanh atanhf atanhl atanl cabs cabsf cabsl cacos cacosf cacosh cacoshf cacoshl cacosl carg cargf cargl casin casinf casinh casinhf casinhl casinl catan catanf catanh catanhf catanhl catanl cbrt cbrtf cbrtl ccos ccosf ccosh ccoshf ccoshl ccosl ceil ceilf ceill cexp cexpf cexpl cimag cimagf cimagl clog clogf clogl CMPLX CMPLXF CMPLXL Common mathematical functions complex Complex number arithmetic conj conjf conjl copysign copysignf copysignl cos cosf cosh coshf coshl cosl cpow cpowf cpowl cproj cprojf cprojl creal crealf creall csin csinf csinh csinhf csinhl csinl csqrt csqrtf csqrtl ctan ctanf ctanh ctanhf ctanhl ctanl div double_t erf erfc erfcf erfcl erff erfl exp exp2 exp2f exp2l expf expl expm1 expm1f expm1l fabs fabsf fabsl fdim feclearexcept fegetenv fegetexceptflag fegetround feholdexcept feraiseexcept fesetenv fesetexceptflag fesetround fetestexcept feupdateenv FE_ALL_EXCEPT FE_DFL_ENV FE_DIVBYZERO FE_DOWNWARD FE_INEXACT FE_INVALID FE_OVERFLOW FE_TONEAREST FE_TOWARDZERO FE_UNDERFLOW FE_UPWARD Floating-point environment float_t floor floorf floorl fma fmaf fmal fmax fmaxf fmaxl fmin fminf fminl fmod fmodf fmodl fpclassify FP_INFINITE FP_NAN FP_NORMAL FP_SUBNORMAL FP_ZERO frexp frexpf frexpl HUGE_VAL HUGE_VALF HUGE_VALL hypot hypotf hypotl I ilogb ilogbf ilogbl imaginary imaxabs imaxdiv INFINITY isfinite isgreater isgreaterequal isinf isless islessequal islessgreater isnan isnormal isunordered labs ldexp ldexpf ldexpl ldiv lgamma lgammaf lgammal llabs lldiv llrint llrintf llrintl llround llroundf llroundl log log10 log10f log10l log1p log1pf log1pl log2 log2f log2l logb logbf logbl logf logl lrint lrintf lrintl lround lroundf lroundl MATH_ERREXCEPT math_errhandling MATH_ERRNO modf modff modfl nan NAN nanf nanl nearbyint nearbyintf nearbyintl nextafter nextafterf nextafterl nexttoward nexttowardf nexttowardl Numerics pow powf powl Pseudo-random number generation rand RAND_MAX remainder remainderf remainderl remquo remquof remquol rint rintf rintl round roundf roundl scalbln scalblnf scalblnl scalbn scalbnf scalbnl signbit sin sinf sinh sinhf sinhl sinl sqrt sqrtf sqrtl srand tan tanf tanh tanhf tanhl tanl tgamma tgammaf tgammal trunc truncf truncl Type-generic math _Complex_I _Imaginary_I Program support abort atexit at_quick_exit exit EXIT_FAILURE EXIT_SUCCESS getenv getenv_s jmp_buf longjmp Program support utilities quick_exit raise setjmp SIGABRT SIGFPE SIGILL SIGINT signal SIGSEGV SIGTERM sig_atomic_t SIG_DFL SIG_ERR SIG_IGN system _Exit Strings atof atoi atol atoll btowc c16rtomb c32rtomb char16_t char32_t isalnum isalpha isblank iscntrl isdigit isgraph islower isprint ispunct isspace isupper iswalnum iswalpha iswblank iswcntrl iswctype iswdigit iswgraph iswlower iswprint iswpunct iswspace iswupper iswxdigit isxdigit mblen mbrlen mbrtoc16 mbrtoc32 mbrtowc mbsinit mbsrtowcs mbsrtowcs_s mbstate_t mbstowcs mbstowcs_s mbtowc memchr memcmp memcpy memcpy_s memmove memmove_s memset memset_s Null-terminated byte strings Null-terminated multibyte strings Null-terminated wide strings strcat strcat_s strchr strcmp strcoll strcpy strcpy_s strcspn strerror strerrorlen_s strerror_s Strings library strlen strncat Thread support call_once cnd_broadcast cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait mtx_destroy mtx_init mtx_lock mtx_plain mtx_recursive mtx_timed mtx_timedlock mtx_trylock mtx_unlock once_flag ONCE_FLAG_INIT thrd_busy thrd_create thrd_current thrd_detach thrd_equal thrd_error thrd_exit thrd_join thrd_nomem thrd_sleep thrd_success thrd_timedout thrd_yield Thread support library thread_local tss_create tss_delete TSS_DTOR_ITERATIONS tss_get tss_set Type support Boolean type support library Fixed width integer types FLT_EVAL_METHOD FLT_ROUNDS max_align_t NULL Numeric limits offsetof ptrdiff_t size_t Type support Variadic functions Variadic functions va_arg va_copy va_end va_list va_start
characters

函數(shù)定義將函數(shù)體(聲明和語句序列)與函數(shù)名稱和參數(shù)列表關(guān)聯(lián)起來。與函數(shù)聲明不同,函數(shù)定義只允許在文件范圍內(nèi)(沒有嵌套函數(shù))。

C支持兩種不同形式的函數(shù)定義:

specifiers-and-qualifiers parameter-list-declarator function-body

(1)


specifiers-and-qualifiers identifier-list-declarator declaration-list function-body

(2)


其中

符和限定符

-

類型說明符的組合,可能被聲明器修改,形成返回類型存儲類說明符,它確定標(biāo)識符(靜態(tài),外部或無)與inline,noreturn或none

參數(shù)列表說明符

-

一個函數(shù)類型的聲明符,它使用參數(shù)列表來指定函數(shù)參數(shù)

標(biāo)識符列表說明符

-

一個函數(shù)類型的聲明符,它使用標(biāo)識符列表來指定函數(shù)參數(shù)

聲明列表

-

在identifier-list-declarator中聲明每個標(biāo)識符的聲明序列。這些聲明不能使用初始化器,唯一允許的存儲類說明符是寄存器。

功能體

-

一個復(fù)合語句,它是一個括號括起來的聲明和語句序列,每當(dāng)調(diào)用該函數(shù)時都會執(zhí)行

  • 可能由聲明者修改的類型說明符構(gòu)成返回類型

  • 存儲類說明符,其中確定所述識別符的鍵(staticextern或無)

  • 函數(shù)說明符inline,noreturn或none

 parameter-list-declarator   -   a declarator for a function type which uses a [parameter list](function_declaration) to designate function parameters     identifier-list-declarator   -   a declarator for a function type which uses a [identifier list](function_declaration) to designate function parameters     declaration-list   -   sequence of declarations that declare every identifier in identifier-list-declarator. These declarations cannot use initializers and the only [storage-class specifier](storage_duration) allowed is `register`.     function-body   -   a [compound statement](statements#Compound_statements), that is a brace-enclosed sequence of declarations and statements, that is executed whenever this function is called

1)新式(C89)功能定義。該定義既引入了函數(shù)本身,又作為未來函數(shù)調(diào)用表達(dá)式的函數(shù)原型,強(qiáng)制從參數(shù)表達(dá)式轉(zhuǎn)換為聲明的參數(shù)類型。

int max(int a, int b){    return a>b?a:b;}
 double g(void){    return 0.1;}

2)舊式(K&R)功能定義。這個定義不像原型,任何未來的函數(shù)調(diào)用表達(dá)式都會執(zhí)行默認(rèn)參數(shù)促銷。

int max(a, b)int a, b;{    return a>b?a:b;}double g(){    return 0.1;}

說明

與函數(shù)聲明一樣,函數(shù)的返回類型由聲明符中的類型說明符確定,并可能在聲明中像通常一樣由聲明器修改,這些類型必須是完整的非數(shù)組對象類型或類型void。

void f(char *s) { puts(s); } // return type is voidint sum(int a, int b) { return a+b: } // return type is intint (*foo(const void *p))[3] { // return type is pointer to array of 3 int    return malloc(sizeof(int[3]));}

和函數(shù)聲明一樣,參數(shù)的類型從函數(shù)調(diào)整到指針,從數(shù)組到指針,為了構(gòu)造函數(shù)類型,它們的頂級限定符被去除。

與函數(shù)聲明不同,未命名的形式參數(shù)是不允許的,即使它們沒有在函數(shù)中使用,它們也必須被命名。唯一的例外是特殊參數(shù)列表(void)。

int f(int, int); // declaration// int f(int, int) { return 7; } // Errorint f(int a, int b) { return 7; } // definitionint g(void) { return 8; } // OK, void doesn't declare a parameter

在函數(shù)體內(nèi),每個參數(shù)都是一個左值表達(dá)式,它們具有自動存儲持續(xù)時間和塊范圍。內(nèi)存中的參數(shù)布局(或者如果它們存儲在內(nèi)存中)未指定:它是調(diào)用約定的一部分。

int main(int ac, char **av){
    ac = 2; // parameters are lvalues
    av = (char *[]){"abc", "def", NULL};    f(ac, av);}

有關(guān)函數(shù)調(diào)用機(jī)制的其他詳細(xì)信息,請參閱函數(shù)調(diào)用運(yùn)算符,然后返回以從函數(shù)返回。

__func__在每個函數(shù)體中,可以使用具有塊范圍和靜態(tài)存儲持續(xù)時間的特殊預(yù)定義變量__func__,就像在緊跟在大括號之后定義的那樣。static const char __func __ [] =“function name”; 這個特殊的標(biāo)識符有時與預(yù)定義的宏常量__FILE__和__LINE__結(jié)合使用,例如通過assert。

(自C99以來)

筆記

參數(shù)列表必須明確地出現(xiàn)在聲明器中,它不能從 typedef 繼承。

typedef int p(int q, int r); // p is a function type int(int, int)p f { return q + r; } // Error

在C89中,說明符和限定符是可選的,如果省略,函數(shù)的返回類型默認(rèn)為int(可能由聲明者修改)。另外,舊式定義不需要聲明列表中的每個參數(shù)。任何聲明缺失的參數(shù)都有int類型。max(a,b)// a和b的類型是int,返回類型是int {return a> b?a:b; }

(直到C99)

參考

  • C11 standard (ISO/IEC 9899:2011):

    • 6.9.1 Function definitions (p: 156-158)

  • C99 standard (ISO/IEC 9899:1999):

    • 6.9.1 Function definitions (p: 141-143)

  • C89/C90 standard (ISO/IEC 9899:1990):

    • 3.7.1 Function definitions

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