configure: error: Building GCC requires GMP 4.2+, MPFR 2.4.0+ and MPC 0.8.0+.

cd gmp-6.1.2/mkdir  gmp-6.1.2-build
cd gmp-6.1.2-build
../configure

checking for suitable m4... configure: error: No usable m4 in $PATH or /usr/5bin (see config.log for reasons).

cd m4-1.4.18mkdir m4-1.4.18-buildcd m4-1.4.18-build../configuremakesudo make install

cd ../../gmp-6.1.2 /gmp-6.1.2-build../configuremakesudo make install

cd ../../mpfr-3.1.6mkdir mpfr-3.1.6-buildcd mpfr-3.1.6-build../configuremakesudo make install

cd ../../mpc-1.0.3mkdir mpc-1.0.3-buildcd mpc-1.0.3-build../configuremakesudo make install

cd ../../gcc-7.2.0mkdir gcc-7.2.0-buildcd gcc-7.2.0-build../configure

configure: error: I suspect your system does not have 32-bit development libraries (libc and headers). If you have them, rerun configure with --enable-multilib. If you do not have them, and want to build a 64-bit-only compiler, rerun configure with –disable-multilib.

../configure --enable-multilibmake

checking dynamic linker characteristics... configure: error: Link tests are not allowed after GCC_NO_EXECUTABLES.
Makefile:11923: recipe for target 'configure-stage1-zlib' failed
make[2]: *** [configure-stage1-zlib] Error 1
make[2]: Leaving directory '/home/wangzhi/桌面/gcc-7.2.0/gcc-7.2.0-build'
Makefile:23803: recipe for target 'stage1-bubble' failed
make[1]: *** [stage1-bubble] Error 2
make[1]: Leaving directory '/home/wangzhi/桌面/gcc-7.2.0/gcc-7.2.0-build'
Makefile:933: recipe for target 'all' failed
make: *** [all] Error 2

make distclean../configure –enable-multilibmake

sudo apt-get install gawksudo apt-get install gcc-multilib
sudo apt-get install binutils
sudo apt-get install lzipmake distclean../configuremakesudo make install

/* ISO C1X: 7.15 Alignment <stdalign.h>.  */#ifndef _STDALIGN_H
#define _STDALIGN_H#ifndef __cplusplus#define alignas _Alignas
#define alignof _Alignof#define __alignas_is_defined 1
#define __alignof_is_defined 1#endif#endif    /* stdalign.h */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdalign.h>#define _INT_NAME   (128)struct names {int len;char name[];
};struct people {int id;alignas(struct names) char name[sizeof(struct names) + _INT_NAME];
};static void test_aligned(void) {printf("sizeof(struct people) = %zu.\n", sizeof(struct people));// 控制内存布局struct people pe = { 1 };struct names * name = (struct names *)pe.name;name->len = _INT_NAME;strcpy(name->name, "你好吗？");printf("people len = %d, name = %s.\n", pe.id, name->name);// 测试内存对其printf("alignof(struct people) = %zu.\n", alignof(struct people));// 接着控制内存布局alignas(struct names) char xname[sizeof(struct names) + _INT_NAME];struct names * xna = (struct names *)xname;strcpy(xna->name, "我还行！");//// 另一种内存申请, 一种演示， malloc已经够额// aligned_alloc 相比 malloc 多了第一个参数， 这个参数必须是2的幂// 在特定嵌入式平台会使用//
    void * ptr = aligned_alloc(alignof(struct names), _INT_NAME);if (NULL == ptr)exit(EXIT_FAILURE);free(ptr);
}

#include <stdio.h>
#include <stdlib.h>_Noreturn static void _test(void) {puts("func _test C11 never returns");abort();
}int main(int argc, char * argv[]) {_test();
}

#include <stdio.h>void sort_insert_int(int a[], int len);
void sort_insert_float(float a[], int len);
void sort_insert_double(double a[], int len);#define sort_insert(a, len) \_Generic(a, \int *    : sort_insert_int, \float *  : sort_insert_float, \double * : sort_insert_double)(a, len)//
// file     : generic.c
// test     : C11 泛型用法
//
int main(int argc, char * argv[]) {int a[] = { 1, 2, 5, 3, 4, 11, 23, 34, 33, 55, 11, 12 };int i, len = sizeof a / sizeof (*a);sort_insert(a, len);for (i = 0; i < len; ++i)printf("%2d ", a[i]);putchar('\n');return 0;
}#define sort_insert_definition(T) \void \sort_insert_##T (T a[], int len) { \int i, j; \for (i = 1; i < len; ++i) { \T key = a[j = i]; \while (j > 0 && a[j - 1] < key) { \a[j] = a[j - 1]; \--j; \} \a[j] = key; \} \}sort_insert_definition(int)
sort_insert_definition(float)
sort_insert_definition(double)

#include <stdio.h>int main(void) {printf("C version : %ld.\n", __STDC_VERSION__);_Static_assert(__STDC_VERSION__ < 201112L, "It is c11 version");return 0;
}

#if __STDC_VERSION__ >= 201112L
#   error "It is c11 version"
#endif

_Success_(return != 0)
_ACRTIMP char* __cdecl gets_s(_Out_writes_z_(_Size) char*   _Buffer,_In_                  rsize_t _Size);

#if __STDC_WANT_SECURE_LIB__typedef size_t rsize_t;
#endif#if __STDC_WANT_SECURE_LIB__#ifndef RSIZE_MAX#define RSIZE_MAX (SIZE_MAX >> 1)#endif
#endif

struct cjson {struct cjson * next;struct cjson * child;unsigned char type; char * key;     union {char * vs;double vd;};
};

include <stdatomic.h>// 标记类型, init lock
atomic_flag flag = ATOMIC_FLAG_INIT;// 尝试设置占用(原子操作), try lock
atomic_flag_test_and_set(&flag);// 释放(原子操作), unlock
atomic_flag_clear(&flag);

//
// uchar.h
//
//      Copyright (c) Microsoft Corporation. All rights reserved.
//

#pragma once
#define _UCHAR#include <corecrt.h>_CRT_BEGIN_C_HEADER#define __STDC_UTF_16__
#define __STDC_UTF_32__typedef unsigned short _Char16_t;
typedef unsigned int _Char32_t;#if !defined __cplusplus || (defined _MSC_VER && _MSC_VER < 1900)typedef unsigned short char16_t;typedef unsigned int char32_t;
#endif_Check_return_ _ACRTIMP size_t __cdecl mbrtoc16(_Out_opt_ char16_t *_Pc16, _In_reads_or_z_opt_(_N) const char *_S, _In_ size_t _N, _Inout_ mbstate_t *_Ps);
_Check_return_ _ACRTIMP size_t __cdecl c16rtomb(_Out_writes_opt_(6) char *_S, _In_ char16_t _C16, _Inout_ mbstate_t *_Ps);_Check_return_ _ACRTIMP size_t __cdecl mbrtoc32(_Out_opt_ char32_t *_Pc32, _In_reads_or_z_opt_(_N) const char *_S, _In_ size_t _N, _Inout_ mbstate_t *_Ps);
_Check_return_ _ACRTIMP size_t __cdecl c32rtomb(_Out_writes_opt_(6) char *_S, _In_ char32_t _C32, _Inout_ mbstate_t *_Ps);_CRT_END_C_HEADER/** Copyright (c) 1992-2013 by P.J. Plauger.  ALL RIGHTS RESERVED.* Consult your license regarding permissions and restrictions.V6.40:0009 */

#include <stdio.h>
#include <uchar.h>
#include <locale.h>
#include <string.h>//
// uchar test
//
int main(int argc, char * argv[]) {size_t i, len;const char * str = u8"z\u00df\u6c34\U0001F34C"; // 或 u8"zß水?"
setlocale(LC_ALL, "en_US.utf8");len = strlen(str);printf("Processing %zu bytes: [ ", len);for (i = 0; i < len; ++i) {// 强转是画龙点睛之笔printf("0x%x ", (unsigned char)str[i]);    }printf("]\n");size_t rc;char16_t c16;mbstate_t state = { 0 };const char * ptr = str, * end = str + len;/*//// mbrtoc16 : UTF-8 转换为 UTF-16// _Pc16     -     指向将写入产生的 16-bit 宽字符的位置的指针// _S        -     指向用作输入的多字节字符串的指针// _N         -     能检验的字节数上的限制// _Ps         -     指向转译多字节字符串时所用转换状态对象的指针 // return    :    //                若从 s 转换的字符是空字符（并存储于 *pc16 ，若它非空），则为 0 。//                成功从 s 转换的多字节字符的字节数 [1...n] 。//                若下个 char16_t 组成多 char16_t 字符，并已写入 *pc16 ，则为 -3 。此情况下不从输入处理字节。//                若接下来 n 个字符组成不完整，但到此还合法的多字节字符，则为 -2 。不写入 *pc16 。//                若出现编码错误则为 -1 。不写入 *pc16 ，存储值 EILSEQ 于 errno ，且 *ps 状态未指定。 //size_t __cdecl mbrtoc16(char16_t * _Pc16, const char * _S, size_t _N, mbstate_t * _Ps);
*/while ((rc = mbrtoc16(&c16, ptr, end - ptr + 1, &state))) {printf("Next UTF-16 char: 0x%x  obtained from ", c16);if (rc == (size_t)-3)printf("earlier surrogate pair\n");else if (rc <= ((size_t)-1) / 2) {printf("%zu bytes [ ", rc);for (i = 0; i < rc; ++i)printf("0x%x ", (unsigned char)ptr[i]);    printf("]\n");ptr += rc;} else break;}return 0;
}

#define complex        _Complex/* Narrowest imaginary unit.  This depends on the floating-pointevaluation method.XXX This probably has to go into a gcc related file.  */
#define _Complex_I    (__extension__ 1.0iF)/* Another more descriptive name is `I'.XXX Once we have the imaginary support switch this to _Imaginary_I.  */
#undef I
#define I _Complex_I#if defined __USE_ISOC11 && __GNUC_PREREQ (4, 7)
/* Macros to expand into expression of specified complex type.  */
# define CMPLX(x, y) __builtin_complex ((double) (x), (double) (y))
# define CMPLXF(x, y) __builtin_complex ((float) (x), (float) (y))
# define CMPLXL(x, y) __builtin_complex ((long double) (x), (long double) (y))
#endif

#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
/* Versions of DECIMAL_DIG for each floating-point type.  */
#undef FLT_DECIMAL_DIG
#undef DBL_DECIMAL_DIG
#undef LDBL_DECIMAL_DIG
#define FLT_DECIMAL_DIG        __FLT_DECIMAL_DIG__
#define DBL_DECIMAL_DIG        __DBL_DECIMAL_DIG__
#define LDBL_DECIMAL_DIG    __DECIMAL_DIG__/* Whether types support subnormal numbers.  */
#undef FLT_HAS_SUBNORM
#undef DBL_HAS_SUBNORM
#undef LDBL_HAS_SUBNORM
#define FLT_HAS_SUBNORM        __FLT_HAS_DENORM__
#define DBL_HAS_SUBNORM        __DBL_HAS_DENORM__
#define LDBL_HAS_SUBNORM    __LDBL_HAS_DENORM__/* Minimum positive values, including subnormals.  */
#undef FLT_TRUE_MIN
#undef DBL_TRUE_MIN
#undef LDBL_TRUE_MIN
#define FLT_TRUE_MIN    __FLT_DENORM_MIN__
#define DBL_TRUE_MIN    __DBL_DENORM_MIN__
#define LDBL_TRUE_MIN    __LDBL_DENORM_MIN__#endif /* C11 */

#ifndef _CRT_NO_TIME_Tstruct timespec{time_t tv_sec;  // Seconds - >= 0long   tv_nsec; // Nanoseconds - [0, 999999999]
    };
#endif// The number of clock ticks per second
#define CLOCKS_PER_SEC  ((clock_t)1000)#define TIME_UTC 1_Check_return_
static __inline int __CRTDECL timespec_get(_Out_ struct timespec* const _Ts,_In_  int              const _Base)
{return _timespec64_get((struct _timespec64*)_Ts, _Base);
}

#include <stdio.h>
#include <time.h>//
// struct timespec heoo
//
int main(void) {struct tm tm;struct timespec ts;timespec_get(&ts, TIME_UTC);printf("time_t tv_sec = %lld, long   tv_nsec = %d.\n", (long long)ts.tv_sec, ts.tv_nsec);// 线程不安全, 单纯为了测试tm = *localtime(&ts.tv_sec);printf("now %s", asctime(&tm));    return 0;
}