VS编译动态库的时候没有生成对应的lib文件

由于windows在动态链接的时候,必须从dll文件对应的lib文件里面寻找可链接程序的标志符,因此当你编译生成一个动态库的时候,必须生成相应的lib文件。

有两种方法,一种是

1、在命令行执行:
dumpbin /exports yourdll.dll > yourdll.def

2、编辑 yourdll.def 文件,使之格式与.def文件格式一致。比如:

EXPORTS;
fn1;
fn2;

3、在命令行执行:

lib /def:yourdll.def /machine:i386 /out:yourdll.lib

下面是sqlite3的def文件,其实就是你要导出的函数的名字。

EXPORTS
sqlite3_aggregate_context
sqlite3_aggregate_count
sqlite3_auto_extension
sqlite3_backup_finish
sqlite3_backup_init
sqlite3_backup_pagecount
sqlite3_backup_remaining
sqlite3_backup_step
sqlite3_bind_blob
sqlite3_bind_double
sqlite3_bind_int
sqlite3_bind_int64
sqlite3_bind_null
sqlite3_bind_parameter_count
sqlite3_bind_parameter_index
sqlite3_bind_parameter_name
sqlite3_bind_text
sqlite3_bind_text16
sqlite3_bind_value
sqlite3_bind_zeroblob
sqlite3_blob_bytes
sqlite3_blob_close
sqlite3_blob_open
sqlite3_blob_read
sqlite3_blob_reopen
sqlite3_blob_write
sqlite3_busy_handler
sqlite3_busy_timeout
sqlite3_changes
sqlite3_clear_bindings
sqlite3_close
sqlite3_collation_needed
sqlite3_collation_needed16
sqlite3_column_blob
sqlite3_column_bytes
sqlite3_column_bytes16
sqlite3_column_count
sqlite3_column_database_name
sqlite3_column_database_name16
sqlite3_column_decltype
sqlite3_column_decltype16
sqlite3_column_double
sqlite3_column_int
sqlite3_column_int64
sqlite3_column_name
sqlite3_column_name16
sqlite3_column_origin_name
sqlite3_column_origin_name16
sqlite3_column_table_name
sqlite3_column_table_name16
sqlite3_column_text
sqlite3_column_text16
sqlite3_column_type
sqlite3_column_value
sqlite3_commit_hook
sqlite3_compileoption_get
sqlite3_compileoption_used
sqlite3_complete
sqlite3_complete16
sqlite3_config
sqlite3_context_db_handle
sqlite3_create_collation
sqlite3_create_collation16
sqlite3_create_collation_v2
sqlite3_create_function
sqlite3_create_function16
sqlite3_create_function_v2
sqlite3_create_module
sqlite3_create_module_v2
sqlite3_data_count
sqlite3_db_config
sqlite3_db_handle
sqlite3_db_mutex
sqlite3_db_status
sqlite3_declare_vtab
sqlite3_enable_load_extension
sqlite3_enable_shared_cache
sqlite3_errcode
sqlite3_errmsg
sqlite3_errmsg16
sqlite3_exec
sqlite3_expired
sqlite3_extended_errcode
sqlite3_extended_result_codes
sqlite3_file_control
sqlite3_finalize
sqlite3_free
sqlite3_free_table
sqlite3_get_autocommit
sqlite3_get_auxdata
sqlite3_get_table
sqlite3_global_recover
sqlite3_initialize
sqlite3_interrupt
sqlite3_last_insert_rowid
sqlite3_libversion
sqlite3_libversion_number
sqlite3_limit
sqlite3_load_extension
sqlite3_log
sqlite3_malloc
sqlite3_memory_alarm
sqlite3_memory_highwater
sqlite3_memory_used
sqlite3_mprintf
sqlite3_mutex_alloc
sqlite3_mutex_enter
sqlite3_mutex_free
sqlite3_mutex_leave
sqlite3_mutex_try
sqlite3_next_stmt
sqlite3_open
sqlite3_open16
sqlite3_open_v2
sqlite3_os_end
sqlite3_os_init
sqlite3_overload_function
sqlite3_prepare
sqlite3_prepare16
sqlite3_prepare16_v2
sqlite3_prepare_v2
sqlite3_profile
sqlite3_progress_handler
sqlite3_randomness
sqlite3_realloc
sqlite3_release_memory
sqlite3_reset
sqlite3_reset_auto_extension
sqlite3_result_blob
sqlite3_result_double
sqlite3_result_error
sqlite3_result_error16
sqlite3_result_error_code
sqlite3_result_error_nomem
sqlite3_result_error_toobig
sqlite3_result_int
sqlite3_result_int64
sqlite3_result_null
sqlite3_result_text
sqlite3_result_text16
sqlite3_result_text16be
sqlite3_result_text16le
sqlite3_result_value
sqlite3_result_zeroblob
sqlite3_rollback_hook
sqlite3_rtree_geometry_callback
sqlite3_set_authorizer
sqlite3_set_auxdata
sqlite3_shutdown
sqlite3_sleep
sqlite3_snprintf
sqlite3_soft_heap_limit
sqlite3_soft_heap_limit64
sqlite3_sourceid
sqlite3_sql
sqlite3_status
sqlite3_step
sqlite3_stmt_readonly
sqlite3_stmt_status
sqlite3_strnicmp
sqlite3_table_column_metadata
sqlite3_test_control
sqlite3_thread_cleanup
sqlite3_threadsafe
sqlite3_total_changes
sqlite3_trace
sqlite3_transfer_bindings
sqlite3_update_hook
sqlite3_uri_parameter
sqlite3_user_data
sqlite3_value_blob
sqlite3_value_bytes
sqlite3_value_bytes16
sqlite3_value_double
sqlite3_value_int
sqlite3_value_int64
sqlite3_value_numeric_type
sqlite3_value_text
sqlite3_value_text16
sqlite3_value_text16be
sqlite3_value_text16le
sqlite3_value_type
sqlite3_vfs_find
sqlite3_vfs_register
sqlite3_vfs_unregister
sqlite3_vmprintf
sqlite3_vsnprintf
sqlite3_vtab_config
sqlite3_vtab_on_conflict
sqlite3_wal_autocheckpoint
sqlite3_wal_checkpoint
sqlite3_wal_checkpoint_v2
sqlite3_wal_hook
sqlite3_win32_mbcs_to_utf8
sqlite3_win32_utf8_to_mbcs

第二种就是在你要到处的函数的前面加

extern "c" void __declspec ( dllexport ) CallC( char * szText){
std::cout << szText << std::endl;
}

void __declspec ( dllexport ) CallC( char * szText){
std::cout << szText << std::endl;
}
void __declspec ( dllexport ) __stdcall CallStd( char * szText){
std::cout << szText << std::endl;
}
具体好像他们又有区别,希望知道的朋友能给解释下,我也不是很清楚了,我当时就这么用,然后我的问题搞定了,看了一些资料,也没搞得很明白,具体有一段英文的好像写的还比较明白了 一起贴下面了。

Stdcall and DLL tools of MSVC and MinGW

The __stdcall calling convention has been there for a very longtime. While older calling conventions like __pascal fell intooblivion,__stdcall became the standard calling convention of Win32API functions. Unlike __cdecl (the native calling conventionof C/C++),it is supported in C/C++,Visual Basic,Java,and other languagesalike,which makes it the first choice when building a DLL for cross-languageuse.

The internal representations of both __cdecl and __stdcallfunctions have decorations. In MSVC (Microsoft Visual C++) and MinGW(Minimalistic GNU for Windows) GCC,__cdecl function will be prefixedan underscore,and __stdcall functions will have the beginning underscoreas well as be appended by the at-sign (@) followed by the numberof bytes in the argument list. So,double __cdecl sin(double)will be decorated as _sin,and double __stdcall sin(double)will be decorated as _sin@8.

But things are not that simple. The decorations could change when theyappear in DLLs or when they are produced by different compilers. The followingtable lists the names as are produced by MSVC,MinGW,Digital Mars C/C++Compiler (DMC),Borland C++ Compiler/C++ Builder (BCC):

Calling Convention Internal* MSVC DLL (w/ DEF) MSVC DLL (dllexport) DMC DLL MinGW DLL BCC DLL
__stdcall _Function@n Function _Function@n _Function@n Function@n Function
__cdecl _Function Function Function Function Function _Function

* For all but BCC,which has the same namingconvention for symbols in code and exported name in DLL.

What a mess (especially when you notice that,for MSVC,whether aname is exported by a DEF file or by the __declspec(dllexport) attribute affects itsnaming decoration)! And although the ending decoration clearly shows howmany bytes the called function pops up from stack before returning,it isnot necessarily the most frequently used form. E.g.,the Win32 APIfunctions in the system DLLs have no decoration at all,as in the caseones uses a DEF file when exporting functions with MSVC. Many DLLsintended for multi-language usage also follow this practice and use nodecoration with __stdcall functions (although the Java NativeInterface,on Win32 platforms,will accept functions either undecoratedor decorated in the Microsoft way,the latter being the preferredform). The remaining part of this article is thus devoted to thecreation and use of such DLLs with MSVC and MinGW,as well as theintroduction and comparison of related tools (there are good articles athttp://www.bcbdev.com/articles.htmexplaining the complexities of DLLs with Borland C++ Builder,so I neednot bother to say anything more about it).

Tools working with DEF files

First,I will talk about the DEF file format and the relevant tools usedwith MSVC and MinGW. Many intricacies lie here.

DEF file format

We care about only two sections of the DEF file: the LIBRARY section andthe EXPORTS section. The LIBRARY section specifies the internal name ofthe DLL; and the EXPORTS section specifies the function or data items toexport. A short example follows:
LIBRARY testdll.dll
EXPORTS
 cdeclFunction @1
 _stdcallFunction@8 @2
 aliasName = cdeclFunction @3
This DEF file defines three exports for a testdll.dll:the first one is a __cdecl function,the second one a __stdcallfunction,and the third one an alias of the first function (the leftside of the "=" sign is an exported name and the right side the internalname). The three functions are also assigned ordinals. A functioncan be called by its name or its ordinal.

CL

CL can accept a DEF file on the command line,and it simply passesthe file name to LINK. E.g.,
cl /LD testdll.obj testdll.def
will become
link /out:testdll.dll /dll /implib:testdll.lib /def:testdll.def testdll.obj

LINK

LINK is our most important tool when treating DLL and DEF fileswith MSVC. The command line mentioned in CL already shows the optionscommonly used when creating a DLL with a DEF file. The main point is: ifwe do not use a DEF file when creating a DLL,the exported name of a __stdcallfunction will be _Function@n; but if we use a DEFfile,the exported name could be either Function or _Function@n;if both names appear,only the undecorated form is used. However,wecan force both forms of exports with the following lines in the EXPORTSsection:
TestFunction = _TestFunction@4
_TestFunction@4 = _TestFunction@4

LIB

If we have the DLL from somebody else (no source available),and we havethe DEF file,the easiest way to create an import library is to use the LIBtool. The following syntax is often enough (check MSDNfor more details):
lib /def:DEF_file
Nota bene: 1) it seems LIB does not accept aliased forms(it will simply ignore the part after the equal-sign); 2) it assumes allfunctions in the DEF file __cdecl. The second point lies in thefact that the import library it produces will map each symbol in the DLLto an internal name with an underscore prefixed,i.e.,the linker usingthe import library will try to resolve an undefined symbol _Functionto the symbol Function in the DLL. It takes no special care ofthe __stdcall calling convention. With some techniques we coulduse LIB to produce import libraries for __stdcall functions,but the caller could only call them by ordinal,not by name. The detailsare left as an exercise :-) .

gcc

Here we use gcc to call ld. The reason why we do not use lddirectly is that using gcc is generally more convenient. The -shared option is specially designed to produce DLLs. We could also use the -Wl option to pass special link options.

ld

GNU ld has many options regarding DLLs,but we shall only focuson four (help information follows):
--add-stdcall-alias Export symbols with and without @nn
--kill-at Remove @nn from exported symbols
--out-implib <file> Generate import library
--output-def <file> Generate a .DEF file for the built DLL
Either gcc or ld can accept a DEF file directly on the commandline. When a function (say,TestFunction@4) is marked as __declspec(dllexport),and we have the following line in theEXPORTS section,
TestFunction = TestFunction@4
both symbols will be exported to the DLL ( LINK has similarbehaviour too). This behaviour is different from dllwrap,whichwe shall talk of immediately.

dllwrap

GNU dllwrap could produce a DLL by a DEF file. We generally use dllwrapin the following syntax,
dllwrap --def DEF_file -o DLL_file OBJ_files [--output-lib LIB_file]
and dllwrap will transparently call gcc, ld,and dlltoolto fulfil its task. If dllwrap is asked to produce an import library ( --output-lib), it will let dlltool do it.Unlike LINK or ld,dllwrap will ignore the export specifications in an object file,and will not export aname unless it is specifically listed as an exported name in the EXPORTSsection (unless one does not use a DEF file at all).

dlltool

GNU dlltool may be used to create the files needed to build anduse dynamic link libraries (DLLs). The following options are of interestto us currently:
-l --output-lib <outname> Generate an interface library.
-D --dllname <name> Name of input dll to put into interface lib.
-d --input-def <deffile> Name of .def file to be read in.
-U --add-underscore Add underscores to symbols in interface library.
-k --kill-at Kill @<n> from exported names.
dlltool works like LIB,and similarly it will ignore the part after the equal-sign in a DEF file,but ithas its special features that somehow compensate for this shortcoming:
  • the -U optionmakes the items in the DEF file map to symbols prefixed with anunderscore in the DLL,and
  • the -k option makes theitems in the DEF file map to symbols stripped of @n inthe DLL.

pexports

This is a stand-alone open-source tool to produce a DEF file from a givenDLL. It is not distributed with MSVC or MinGW,and you may choose to download hereif you do not find it elsewhere.

The __stdcall DLL and the import library

Having learnt so much about the tools,now we are ready to do what we wanted.We still need sed (search on the Internet if you do not alreadyhave this useful tool),and a knowledge of regular expression is requiredto understand thoroughly how it works.

Microsoft Visual C++

The simplest way to produce a DLL is to use the /LD command-lineoption of CL:
cl /LD OBJ_files
The resulting DLL will have exported names like _MyFunction@8,as is shown in the `MSVC DLL (dllexport)' columnabove. To create symbols with no decoration,we must use a DEF file. Thefollowing is an automatic way to create a DEF file from the DLL if __declspec(dllexport) is used to indicate which functions toexport:
link /out:DLL_file /dll OBJ_files
pexports DLL_file | sed "s/^_\([[:alnum:]_]\+\)@[[:digit:]]\+/\1/" > DEF_file
At this step,you may also want to generate a DEF file to make the DLLusable with MinGW source.
pexports DLL_file | sed "s/^_\([[:alnum:]_]\+\)\(@[[:digit:]]\+\)/\1\2/" > DEF_for_gcc
Once you have the object files and the DEF file,creating the DLL and theimport library can be done in one step:
link /out:DLL_file /dll /def:DEF_file /implib:LIB_file OBJ_files
And you are free to use the DLL and the import library now as you wish.

MinGW GCC

If we do not need to control which functions to export except by __declspec(dllexport),we can type:
gcc -shared -o DLL_file OBJ_files -Wl,--output-def,DEF_file
gcc -shared -o DLL_file OBJ_files -Wl,--kill-at
dlltool -d DEF_file --dllname DLL_file --output-lib LIB_file --kill-at
If we want to use a DEF file to control which functions to export,we canstart by (assuming __declspec(dllexport) is used to indicate whichfunctions to export)
gcc -shared -o DLL_file OBJ_files -Wl,--kill-at,DEF_file
to produce a DEF file with exports like " Function =Function@n@Ordinal". After editing it to our will,the following commandswill finish the job:
dllwrap --def DEF_file -o DLL_file OBJ_files
sed "s/[[:alnum:]_]\+ *= *//" DEF_file > New_DEF_file
dlltool -d New_DEF_file --dllname DLL_file --output-lib LIB_file --kill-at
And the import library is now at your hand to use.

I am not sure whether I have stated clearly,but I have listed all myfindings when I struggled to find out how to use the DLL tools properlyand how to deal with __stdcall functions in DLLs. Hope you findit useful.

ACKNOWLEDGEMENT: The MinGW mailing list provided much usefulinformation; Luke Dunstan provided important suggestions and corrections.

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