DLLMain能够执行，但里面的内容不输出的问题，求大神指教！

显示全部楼层 · 2021-1-27 06:52:09

小弟初学DLL编写。环境是Codeblocks10.05，编译器是MinGW。
首先新建一个dll工程，命名为mydll。
mydll.h文件内容：
#ifndef__MYDLL_H__
#define__MYDLL_H__
#include
/*Tousethisexportedfunctionofdll,includethisheader
*inyourproject.
*/
#ifdefBUILD_MY_DLL
#defineDLL_EXPORT__declspec(dllexport)
#else
#defineDLL_EXPORT__declspec(dllimport)
#endif

#ifdef__cplusplus
extern"C"
{
#endif
intDLL_EXPORTsay(constchar*s);
#ifdef__cplusplus
}
#endif
#endif//__MAIN_H__

mydll.cpp文件内容：
#include
#include
#include"mydll.h"
intDLL_EXPORTsay(constchar*s)
{
printf("%s\n",s);
return-1;
}
BOOLWINAPIDllMain(HINSTANCEhinstDLL,DWORDfdwReason,LPVOIDlpvReserved)
{
//MessageBox(NULL,"MessageBoxText(内容)","Title(标题)",MB_OK);
//freopen("OUTPUT.txt","w",stdout);
printf("被调用\n");
switch(fdwReason)
{
caseDLL_PROCESS_ATTACH:
//returnFALSEtofailDLLload
printf("attachtoprocess\n");
break;
caseDLL_PROCESS_DETACH:
printf("detachfromprocess\n");
break;
caseDLL_THREAD_ATTACH:
printf("attachtothread\n");
break;
caseDLL_THREAD_DETACH:
printf("detachtothread\n");
break;
}
returnTRUE;//succesful
}

加入宏BUILD_MY_DLL，编译链接成功，生成mydll.dll动态链接库文件和libmydll.dll.a文件(lib文件)。
使用mydll.dll文件：
新建工程，将mydll.dll文件拷贝到工程目录，main.cpp文件：
/**显式加载DLL中的函数*/
#include
#include
usingnamespacestd;
intmain()
{
typedefint(*DLL_FUNC_PTR)(constchar*s);
DLL_FUNC_PTRfunc=NULL;
HINSTANCEhinst=::LoadLibrary("mydll.dll");
if(hinst==NULL)
{
cout
上述执行成功，输出内容为：
helloworld!
-1
DllMain函数的内容却没有输出，写到文件里也不行，请问大牛们这是什么原因。
分 -->

千问 · 2021-1-27 06:52:09

高深，没看懂

千问 · 2021-1-27 06:52:09

MethodsforDebuggingDLLs
IfyouhavethesourceforboththeDLLandthecallingprogram,opentheprojectforthecallingexecutablefileanddebugtheDLLfromthere.IfyouloadaDLLdynamically,youmustspecifyitintheAdditionalDLLscategoryoftheDebugtabintheProjectSettingsdialogbox.
IfyouhavethesourcefortheDLLonly,opentheprojectthatbuildstheDLL.UsetheDebugtabintheProjectSettingsdialogboxtospecifytheexecutablefilethatcallstheDLL.
YoucanalsodebugaDLLwithoutaproject.Forexample,maybeyoujustpickedupaDLLandsourcecodebutyoudon'thaveanassociatedprojectorworkspace.YoucanusetheOpencommandontheFilemenutoselectthe.DLLfileyouwanttodebug.Thedebuginformationshouldbeineitherthe.DLLortherelated.PDBfile.AfterVisualC++opensthefile,ontheBuildmenuclickStartDebugandGotobegindebugging.
TodebugaDLLusingtheprojectfortheexecutablefile
1.FromtheProjectmenu,clickSettings.
TheProjectSettingsdialogboxappears.
2.ChoosetheDebugtab.
3.IntheCategorydrop-downlistbox,selectGeneral.
4.IntheProgramArgumentstextbox,typeanycommand-lineargumentsrequiredbytheexecutablefile.
5.IntheCategorydrop-downlistbox,selectAdditionalDLLs.
6.IntheLocalNamecolumn,typethenamesofDLLstodebug.
Ifyouaredebuggingremotely,theRemoteNamecolumnappears.Inthiscolumn,typethecompletepathfortheremotemoduletomaptothelocalmodulename.
7.InthePreloadcolumn,selectthecheckboxifyouwanttoloadthemodulebeforedebuggingbegins.
8.ClickOKtostoretheinformationinyourproject.
9.FromtheBuildmenu,clickStartDebugandGotostartthedebugger.
YoucansetbreakpointsintheDLLorthecallingprogram.YoucanopenasourcefilefortheDLLandsetbreakpointsinthatfile,eventhoughitisnotapartoftheexecutablefile'sproject.
TodebugaDLLusingtheprojectfortheDLL
1.FromtheProjectmenu,clickSettings.
TheProjectSettingsdialogboxappears.
2.ChoosetheDebugtab.
3.IntheCategorydrop-downlistbox,selectGeneral.
4.IntheExecutableForDebugSessiontextbox,typethenameoftheexecutablefilethatcallstheDLL.
5.IntheCategorylistbox,selectAdditionalDLLs.
6.IntheLocalModuleNamecolumn,typethenameoftheDLLsyouwanttodebug.
7.ClickOKtostoretheinformationinyourproject.
8.SetbreakpointsasrequiredinyourDLLsourcefilesoronfunctionsymbolsintheDLL.
9.FromtheBuildmenu,clickStartDebugandGotostartthedebugger.
TodebugaDLLcreatedwithanexternalproject
1.FromtheProjectmenu,clickSettings.
TheProjectSettingsdialogboxappears.
2.ChoosetheDebugtab.
3.IntheCategorydrop-downlistbox,selectGeneral.
4.IntheExecutableForDebugSessiontextbox,typethenameoftheDLLthatyourexternalmakefilebuilds.
5.ClickOKtostoretheinformationinyourproject.
6.BuildadebugversionoftheDLLwithsymbolicdebugginginformation,ifyoudon'talreadyhaveone.
7.FollowoneofthetwoproceduresimmediatelyprecedingthisonetodebugtheDLL.

千问 · 2021-1-27 06:52:09

无量天尊,这不是秃子头上的虱子,明摆的嘛,改成:
在mydll.h
#ifdef__cplusplus
extern"C"
{
#endif
intDLL_EXPORTsay(constchar*s);
BOOLWINAPIDllMain(HINSTANCEhinstDLL,DWORDfdwReason,LPVOIDlpvReserved);
#ifdef__cplusplus
}
#endi

千问 · 2021-1-27 06:52:09

loadlibrary或free的时候都会调用dllmain按理说楼主的代码应该会执行的，估计是人品问题了

千问 · 2021-1-27 06:52:09

不放到extern"C"里的话,g++会对dllmain进行符号修饰,所以就无法在loadlibrary时被调用了

千问 · 2021-1-27 06:52:09

说白了,这与编译器也有一定的问题,vc的编译器就不需要!!!

千问 · 2021-1-27 06:52:09

引用5楼wangdahu888的回复:不放到extern"C"里的话,g++会对dllmain进行符号修饰,所以就无法在loadlibrary时被调用了
看来我是忽略了vc的优化了，没注意楼主不是vc