前言
在 C++ 中有个扩展库 ext，里面有一些黑科技（hash, splay, binomial_heap 等等），
在 Windows 环境中，我们运行 Dev-C++ 并在头文件写 #include<bits/extc++.h> 时，经常会收到 [Error] iconv.h: No such file or directory 的编译报错。
所以为了代替他，我们会写很多
#include<ext/pb_ds/hash_policy.hpp> #include<ext/pb_ds/assoc_container.hpp> 诸如此类。这不失为一个解决方案，但是万能头显然更加方便快捷。
现在我们来试着解决这个问题。
Step 1
找到您电脑上头文件的存储位置。通常为 C:Program Files (x86)Dev-CppMinGW64libgccx86_64-w64-mingw324.9.2includec++。
如果找不到可以新建一个 cpp 文件，开头写上 #include<iostream> 然后 Ctrl+左键点一下就可以知道文件目录了。
Step 2
在此目录下新建一个 iconv.h 文件，把下列内容复制进去：
/* Copyright (C) 1999-2019 Free Software Foundation, Inc. This file is part of the GNU LIBICONV Library. The GNU LIBICONV Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU LIBICONV Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU LIBICONV Library; see the file COPYING.LIB. If not, see <https://www.gnu.org/licenses/>. */ /* When installed, this file is called "iconv.h". */ #ifndef _LIBICONV_H #define _LIBICONV_H #define _LIBICONV_VERSION 0x0110 /* version number: (major<<8) + minor */ extern __declspec (dllimport) int _libiconv_version; /* Likewise */ /* We would like to #include any system header file which could define iconv_t, 1. in order to eliminate the risk that the user gets compilation errors because some other system header file includes /usr/include/iconv.h which defines iconv_t or declares iconv after this file, 2. when compiling for LIBICONV_PLUG, we need the proper iconv_t type in order to produce binary compatible code. But gcc's #include_next is not portable. Thus, once libiconv's iconv.h has been installed in /usr/local/include, there is no way any more to include the original /usr/include/iconv.h. We simply have to get away without it. Ad 1. The risk that a system header file does #include "iconv.h" or #include_next "iconv.h" is small. They all do #include <iconv.h>. Ad 2. The iconv_t type is a pointer type in all cases I have seen. (It has to be a scalar type because (iconv_t)(-1) is a possible return value from iconv_open().) */ /* Define iconv_t ourselves. */ #undef iconv_t #define iconv_t libiconv_t typedef void* iconv_t; /* Get size_t declaration. Get wchar_t declaration if it exists. */ #include <stddef.h> /* Get errno declaration and values. */ #include <errno.h> /* Some systems, like SunOS 4, don't have EILSEQ. Some systems, like BSD/OS, have EILSEQ in a different header. On these systems, define EILSEQ ourselves. */ #ifndef EILSEQ #define EILSEQ #endif #ifdef __cplusplus extern "C" { #endif /* Allocates descriptor for code conversion from encoding ‘fromcode’ to encoding ‘tocode’. */ #ifndef LIBICONV_PLUG #define iconv_open libiconv_open #endif extern iconv_t iconv_open (const char* tocode, const char* fromcode); /* Converts, using conversion descriptor ‘cd’, at most ‘*inbytesleft’ bytes starting at ‘*inbuf’, writing at most ‘*outbytesleft’ bytes starting at ‘*outbuf’. Decrements ‘*inbytesleft’ and increments ‘*inbuf’ by the same amount. Decrements ‘*outbytesleft’ and increments ‘*outbuf’ by the same amount. */ #ifndef LIBICONV_PLUG #define iconv libiconv #endif extern size_t iconv (iconv_t cd, char* * inbuf, size_t *inbytesleft, char* * outbuf, size_t *outbytesleft); /* Frees resources allocated for conversion descriptor ‘cd’. */ #ifndef LIBICONV_PLUG #define iconv_close libiconv_close #endif extern int iconv_close (iconv_t cd); #ifdef __cplusplus } #endif #ifndef LIBICONV_PLUG /* Nonstandard extensions. */ #if 1 #if 0 /* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before <wchar.h>. BSD/OS 4.0.1 has a bug: <stddef.h>, <stdio.h> and <time.h> must be included before <wchar.h>. */ #include <stddef.h> #include <stdio.h> #include <time.h> #endif #include <wchar.h> #endif #ifdef __cplusplus extern "C" { #endif /* A type that holds all memory needed by a conversion descriptor. A pointer to such an object can be used as an iconv_t. */ typedef struct { void* dummy1[28]; #if 1 mbstate_t dummy2; #endif } iconv_allocation_t; /* Allocates descriptor for code conversion from encoding ‘fromcode’ to encoding ‘tocode’ into preallocated memory. Returns an error indicator (0 or -1 with errno set). */ #define iconv_open_into libiconv_open_into extern int iconv_open_into (const char* tocode, const char* fromcode, iconv_allocation_t* resultp); /* Control of attributes. */ #define iconvctl libiconvctl extern int iconvctl (iconv_t cd, int request, void* argument); /* Hook performed after every successful conversion of a Unicode character. */ typedef void (*iconv_unicode_char_hook) (unsigned int uc, void* data); /* Hook performed after every successful conversion of a wide character. */ typedef void (*iconv_wide_char_hook) (wchar_t wc, void* data); /* Set of hooks. */ struct iconv_hooks { iconv_unicode_char_hook uc_hook; iconv_wide_char_hook wc_hook; void* data; }; /* Fallback function. Invoked when a small number of bytes could not be converted to a Unicode character. This function should process all bytes from inbuf and may produce replacement Unicode characters by calling the write_replacement callback repeatedly. */ typedef void (*iconv_unicode_mb_to_uc_fallback) (const char* inbuf, size_t inbufsize, void (*write_replacement) (const unsigned int *buf, size_t buflen, void* callback_arg), void* callback_arg, void* data); /* Fallback function. Invoked when a Unicode character could not be converted to the target encoding. This function should process the character and may produce replacement bytes (in the target encoding) by calling the write_replacement callback repeatedly. */ typedef void (*iconv_unicode_uc_to_mb_fallback) (unsigned int code, void (*write_replacement) (const char *buf, size_t buflen, void* callback_arg), void* callback_arg, void* data); #if 1 /* Fallback function. Invoked when a number of bytes could not be converted to a wide character. This function should process all bytes from inbuf and may produce replacement wide characters by calling the write_replacement callback repeatedly. */ typedef void (*iconv_wchar_mb_to_wc_fallback) (const char* inbuf, size_t inbufsize, void (*write_replacement) (const wchar_t *buf, size_t buflen, void* callback_arg), void* callback_arg, void* data); /* Fallback function. Invoked when a wide character could not be converted to the target encoding. This function should process the character and may produce replacement bytes (in the target encoding) by calling the write_replacement callback repeatedly. */ typedef void (*iconv_wchar_wc_to_mb_fallback) (wchar_t code, void (*write_replacement) (const char *buf, size_t buflen, void* callback_arg), void* callback_arg, void* data); #else /* If the wchar_t type does not exist, these two fallback functions are never invoked. Their argument list therefore does not matter. */ typedef void (*iconv_wchar_mb_to_wc_fallback) (); typedef void (*iconv_wchar_wc_to_mb_fallback) (); #endif /* Set of fallbacks. */ struct iconv_fallbacks { iconv_unicode_mb_to_uc_fallback mb_to_uc_fallback; iconv_unicode_uc_to_mb_fallback uc_to_mb_fallback; iconv_wchar_mb_to_wc_fallback mb_to_wc_fallback; iconv_wchar_wc_to_mb_fallback wc_to_mb_fallback; void* data; }; /* Requests for iconvctl. */ #define ICONV_TRIVIALP 0 /* int *argument */ #define ICONV_GET_TRANSLITERATE 1 /* int *argument */ #define ICONV_SET_TRANSLITERATE 2 /* const int *argument */ #define ICONV_GET_DISCARD_ILSEQ 3 /* int *argument */ #define ICONV_SET_DISCARD_ILSEQ 4 /* const int *argument */ #define ICONV_SET_HOOKS 5 /* const struct iconv_hooks *argument */ #define ICONV_SET_FALLBACKS 6 /* const struct iconv_fallbacks *argument */ /* Listing of locale independent encodings. */ #define iconvlist libiconvlist extern void iconvlist (int (*do_one) (unsigned int namescount, const char * const * names, void* data), void* data); /* Canonicalize an encoding name. The result is either a canonical encoding name, or name itself. */ extern const char * iconv_canonicalize (const char * name); /* Support for relocatable packages. */ /* Sets the original and the current installation prefix of the package. Relocation simply replaces a pathname starting with the original prefix by the corresponding pathname with the current prefix instead. Both prefixes should be directory names without trailing slash (i.e. use "" instead of "/"). */ extern void libiconv_set_relocation_prefix (const char *orig_prefix, const char *curr_prefix); #ifdef __cplusplus } #endif #endif #endif /* _LIBICONV_H */ Step 3
保存。再次编译时可以顺利通过。
