How do I use a third-party DLL file in Visual Studio C

Question

I understand that I need to use LoadLibrary    But what other steps do I need to take in order to use a third-party DLL file   I simply jumped into C   and this is the only part that I do not get  as a Java programmer   I am just looking into how I can use a Qt Library and tesseract-ocr  yet the process makes no sense to me and is so difficult to google   How do I tell the compiler of the functions that I am using  Should there be an include file from the third-party vendor

User · Accepted Answer

As everyone else says  LoadLibrary is the hard way to do it  and is hardly ever necessary   The DLL should have come with a  lib file for linking  and one or more header files to  include into your sources   The header files will define the classes and function prototypes that you can use from the DLL   You will need this even if you use LoadLibrary   To link with the library  you might have to add the  lib file to the project configuration under Linker Input Additional Dependencies

User · Answer

To incorporate third-party DLLs into my VS 2008 C   project I did the following  you should be able to translate into 2010  2012 etc       I put the header files in my solution with my other header files  made changes to my code to call the DLLs  functions  otherwise why would we do all this         Then I changed the build to link the LIB code into my EXE  to copy the DLLs into place  and to clean them up when I did a  clean  - I explain these changes below   Suppose you have 2 third-party DLLs  A DLL and B DLL  and you have a stub LIB file for each  A LIB and B LIB  and header files  A H and B H     Create a  lib  directory under your solution directory  e g  using Windows Explorer  Copy your third-party  LIB and  DLL files into this directory    You ll have to make the next set of changes once for each source build target that you use  Debug  Release      Make your EXE dependent on the LIB files   Go to Configuration Properties -  Linker -  Input -  Additional Dependencies  and list your  LIB files there one at a time  separated by spaces   A LIB B LIB Go to Configuration Properties -  General -  Additional Library Directories  and add your  lib  directory to any you have there already   Entries are separated by semicolons    For example  if you already had   SolutionDir fodder there  you change it to   SolutionDir fodder   SolutionDir lib to add  lib    Force the DLLs to get copied to the output directory   Go to Configuration Properties -  Build Events -  Post-Build Event Put the following in for Command Line  for the switch meanings  see  XCOPY     in a DOS window       XCOPY    SolutionDir   lib   DLL    TargetDir    D  K  Y   You can put something like this for Description    Copy DLLs to Target Directory   Excluded From Build should be No  Click OK   Tell VS to clean up the DLLs when it cleans up an output folder     Go to Configuration Properties -  General -  Extensions to Delete on Clean  and click on        add   dll to the end of the list and click OK

User · Answer

I f you re suppsed to be able to use it  then 3rd-party library should have a   lib file as well as a   dll file  You simply need to add the   lib to the list of input file in your project s  Linker  options   This   lib file isn t necessarily a  static  library  which contains code   instead a   lib can be just a file that links your executable to the DLL

User · Answer

You only need to use LoadLibrary if you want to late bind and only resolve the imported functions at runtime  The easiest way to use a third party dll is to link against a  lib     In reply to your edit   Yes  the third party API should consist of a dll and or a lib that contain the implementation and header files that declares the required types  You need to know the type definitions whichever method you use - for LoadLibrary you ll need to define function pointers  so you could just as easily write your own header file instead  Basically  you only need to use LoadLibrary if you want late binding  One valid reason for this would be if you aren t sure if the dll will be available on the target PC

User · Answer

In order to use Qt with dynamic linking you have to specify the lib files  usually qtmaind lib  QtCored4 lib and QtGuid4 lib for the  Debug  configration  in   Properties    Linker    Input    Additional Dependencies    You also have to specify the path where the libs are  namely in Properties    Linker    General    Additional Library Directories   And you need to make the corresponding  dlls are accessible at runtime  by either storing them in the same folder as your  exe or in a folder that is on your path

User · Answer

You only need to use LoadLibrary if you want to late bind and only resolve the imported functions at runtime  The easiest way to use a third party dll is to link against a  lib     In reply to your edit   Yes  the third party API should consist of a dll and or a lib that contain the implementation and header files that declares the required types  You need to know the type definitions whichever method you use - for LoadLibrary you ll need to define function pointers  so you could just as easily write your own header file instead  Basically  you only need to use LoadLibrary if you want late binding  One valid reason for this would be if you aren t sure if the dll will be available on the target PC

User · Answer

To incorporate third-party DLLs into my VS 2008 C   project I did the following  you should be able to translate into 2010  2012 etc       I put the header files in my solution with my other header files  made changes to my code to call the DLLs  functions  otherwise why would we do all this         Then I changed the build to link the LIB code into my EXE  to copy the DLLs into place  and to clean them up when I did a  clean  - I explain these changes below   Suppose you have 2 third-party DLLs  A DLL and B DLL  and you have a stub LIB file for each  A LIB and B LIB  and header files  A H and B H     Create a  lib  directory under your solution directory  e g  using Windows Explorer  Copy your third-party  LIB and  DLL files into this directory    You ll have to make the next set of changes once for each source build target that you use  Debug  Release      Make your EXE dependent on the LIB files   Go to Configuration Properties -  Linker -  Input -  Additional Dependencies  and list your  LIB files there one at a time  separated by spaces   A LIB B LIB Go to Configuration Properties -  General -  Additional Library Directories  and add your  lib  directory to any you have there already   Entries are separated by semicolons    For example  if you already had   SolutionDir fodder there  you change it to   SolutionDir fodder   SolutionDir lib to add  lib    Force the DLLs to get copied to the output directory   Go to Configuration Properties -  Build Events -  Post-Build Event Put the following in for Command Line  for the switch meanings  see  XCOPY     in a DOS window       XCOPY    SolutionDir   lib   DLL    TargetDir    D  K  Y   You can put something like this for Description    Copy DLLs to Target Directory   Excluded From Build should be No  Click OK   Tell VS to clean up the DLLs when it cleans up an output folder     Go to Configuration Properties -  General -  Extensions to Delete on Clean  and click on        add   dll to the end of the list and click OK

User · Answer

In order to use Qt with dynamic linking you have to specify the lib files  usually qtmaind lib  QtCored4 lib and QtGuid4 lib for the  Debug  configration  in   Properties    Linker    Input    Additional Dependencies    You also have to specify the path where the libs are  namely in Properties    Linker    General    Additional Library Directories   And you need to make the corresponding  dlls are accessible at runtime  by either storing them in the same folder as your  exe or in a folder that is on your path

User · Answer

You only need to use LoadLibrary if you want to late bind and only resolve the imported functions at runtime  The easiest way to use a third party dll is to link against a  lib     In reply to your edit   Yes  the third party API should consist of a dll and or a lib that contain the implementation and header files that declares the required types  You need to know the type definitions whichever method you use - for LoadLibrary you ll need to define function pointers  so you could just as easily write your own header file instead  Basically  you only need to use LoadLibrary if you want late binding  One valid reason for this would be if you aren t sure if the dll will be available on the target PC

User · Answer

These are two ways of using a DLL file in Windows    There is a stub library   lib  with associated header files  When you link your executable with the lib-file it will automatically load the DLL file when starting the program  Loading the DLL manually  This is typically what you want to do if you are developing a plugin system where there are many DLL files implementing a common interface  Check out the documentation for LoadLibrary and GetProcAddress for more information on this    For Qt I would suspect there are headers and a static library available that you can include and link in your project

User · Answer

These are two ways of using a DLL file in Windows    There is a stub library   lib  with associated header files  When you link your executable with the lib-file it will automatically load the DLL file when starting the program  Loading the DLL manually  This is typically what you want to do if you are developing a plugin system where there are many DLL files implementing a common interface  Check out the documentation for LoadLibrary and GetProcAddress for more information on this    For Qt I would suspect there are headers and a static library available that you can include and link in your project

User · Answer

I f you re suppsed to be able to use it  then 3rd-party library should have a   lib file as well as a   dll file  You simply need to add the   lib to the list of input file in your project s  Linker  options   This   lib file isn t necessarily a  static  library  which contains code   instead a   lib can be just a file that links your executable to the DLL

User · Answer

I f you re suppsed to be able to use it  then 3rd-party library should have a   lib file as well as a   dll file  You simply need to add the   lib to the list of input file in your project s  Linker  options   This   lib file isn t necessarily a  static  library  which contains code   instead a   lib can be just a file that links your executable to the DLL

User · Answer

In order to use Qt with dynamic linking you have to specify the lib files  usually qtmaind lib  QtCored4 lib and QtGuid4 lib for the  Debug  configration  in   Properties    Linker    Input    Additional Dependencies    You also have to specify the path where the libs are  namely in Properties    Linker    General    Additional Library Directories   And you need to make the corresponding  dlls are accessible at runtime  by either storing them in the same folder as your  exe or in a folder that is on your path

User · Answer

These are two ways of using a DLL file in Windows    There is a stub library   lib  with associated header files  When you link your executable with the lib-file it will automatically load the DLL file when starting the program  Loading the DLL manually  This is typically what you want to do if you are developing a plugin system where there are many DLL files implementing a common interface  Check out the documentation for LoadLibrary and GetProcAddress for more information on this    For Qt I would suspect there are headers and a static library available that you can include and link in your project

User · Answer

In order to use Qt with dynamic linking you have to specify the lib files  usually qtmaind lib  QtCored4 lib and QtGuid4 lib for the  Debug  configration  in   Properties    Linker    Input    Additional Dependencies    You also have to specify the path where the libs are  namely in Properties    Linker    General    Additional Library Directories   And you need to make the corresponding  dlls are accessible at runtime  by either storing them in the same folder as your  exe or in a folder that is on your path

User · Answer

I f you re suppsed to be able to use it  then 3rd-party library should have a   lib file as well as a   dll file  You simply need to add the   lib to the list of input file in your project s  Linker  options   This   lib file isn t necessarily a  static  library  which contains code   instead a   lib can be just a file that links your executable to the DLL

User · Answer

You only need to use LoadLibrary if you want to late bind and only resolve the imported functions at runtime  The easiest way to use a third party dll is to link against a  lib     In reply to your edit   Yes  the third party API should consist of a dll and or a lib that contain the implementation and header files that declares the required types  You need to know the type definitions whichever method you use - for LoadLibrary you ll need to define function pointers  so you could just as easily write your own header file instead  Basically  you only need to use LoadLibrary if you want late binding  One valid reason for this would be if you aren t sure if the dll will be available on the target PC

User · Answer

These are two ways of using a DLL file in Windows    There is a stub library   lib  with associated header files  When you link your executable with the lib-file it will automatically load the DLL file when starting the program  Loading the DLL manually  This is typically what you want to do if you are developing a plugin system where there are many DLL files implementing a common interface  Check out the documentation for LoadLibrary and GetProcAddress for more information on this    For Qt I would suspect there are headers and a static library available that you can include and link in your project

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