I'm beginner in programming. Can somebody please explain (by simple words) what do I have inside the bin directory of program?
What is this PATH environment variable of windows, how does it work (please don't think that I don't know how to use Google, I just want to understand it more clearly)?
You usually put all the binary files for a program in the bin directory. This would be the executable itself and any dlls (dynamic link libraries) that the program uses.
This isn't essential as Windows use the PATH environment variable to look for dlls your program needs. This is a list of folders that Windows searches, in order, when it can't find a dll (say) in the current directory.
So if you want to have a dll used by more than one program you could put it in a location already on the PATH or add a new folder to the PATH.
Related
So I need to triage my PATH environment variable and add extra folders so it can find a certain executable. I was wondering is there a way to mimic how the Windows OS walks all the directories in the path to see if it "reaches" an exe?
I know I could write a program but ideally there is a Windows API call.
PathFindOnPath takes in a file name and returns the fully qualified file path, if the file is found. Note, however, that it also looks in standard directories, in addition to PATH.
... and remove it upon un-installation, of course.
The issue is that other programs being called from my gem need to be able to find a certain file in the system PATH - setting the PATH programatically doesn't work, as these programs are being called in a way that they get a fresh environment.
I tried including these .dll files as "executables" in the gemspec, but that only seems to get some symlink type files in the {ruby}/bin folder, which causes errors because the programs in question are expecting the actual .dll.
As it is, I just have a note in the README asking people to manually copy the .dll files to a folder in the PATH, but it seems like there should be a better way to do this.
Any help would be appreciated - thanks!
I guess the dll is a native lib required by a java class?
If so, you can just put it somewhere in the lib folder and call java.lang.System.load to load it before the java class is used. It doesn't have to be in system PATH this way.
Why doesn't Windows require a full file path when calling LoadLibrary, or for CLSIDs w/ registered DLLs, etc. In what situation would someone benefit from having to fall back on the DLL Search Order to find a dll?
I mean, variables such as %SystemRoot% or %ProgramFiles% could get you to the appropriate folder, and .\ would leave you in your current directory.. So why allow the vagueness?
For explicit linking with GetProcAddress() I would argue that one should use the absolute path to the DLL if at all possible.
For implicit linking with .lib files then the name of the DLL has to be determined at link time which rules out absolute paths.
It is safest to put the DLL in the same directory as the executable, under %Program Files% and protected by UAC, and to use the new DLL search order.
The DLL lookup path, as described in MSDN is:
The directory where the executable module for the current process is located.
The current directory.
The Windows system directory. The GetSystemDirectory function retrieves the path of this directory.
The Windows directory. The GetWindowsDirectory function retrieves the path of this directory.
The directories listed in the PATH environment variable.
Which brings up the following doubt:
Suppose I have an executable in some directory, say: c:\execdir\myexe.exe and it loads a DLL that's found in PATH and is located in c:\dlldir\mydll.dll. Now, suppose mydll.dll tries to load another DLL with LoadLibrary. Which directory will be looked at first - c:\dlldir or c:\execdir?
I think that the lookup rules quoted above say it's going to be c:\execdir because that's allegedly "the directory where the executable module for the current process is located", but it would be nice to get a confirmation from another source.
EDIT: Also, is c:\dlldir\ looked at at all? After all, it's neither where the .exe is located, nor the "current directory" (if that is meant in the general sense).
P.S. I'm interested in both Windows XP and 7.
Yes, it is the executable directory first and it was realised this could lead to a security vulnerability under certain circumstances. There is advice on that page for ensuring your application is not compromised via this mechanism.
I want to put my dependent files in the app directory.
I seem to remember that you can force VB6 to use the files in the local directory only.
Any hints?
You may also want to try setting up Reg-Free COM for your project. There's a freeware called Unattended Make My Manifest that will do most of the work for you.
Placing component libraries in the EXE folder (with or without .local files) can be deleterious to the hygiene of target machines too.
VB6 programs will register the components here via the self-reg entrypoint behind your back if they are not previously registered. Then if the application is moved or removed you leave the user with a broken reigistration - possibly fatal to subsequently installed applications using some of the same components. This is probably fine though for application specific components, i.e. your own DLL or OCX that will never be needed by another application.
The .local trick was really not meant for use with VB6 programs and if it is used your installer needs to be aware and properly install and register the components if they are not already on the machine. It was meant as a manual hack to get around DLL version compatibility problems on individual machines, not a deployment strategy.
Move up to SxS application and assembly manifests (Reg-Free COM and more) for a better solution. DLL/COM Redirection (.local) was a good try but it has many warts.
Clay Nichol's answer about the search order is not quite correct. That search order only applies to non-COM components. I.e. only some DLLs, and not OCXs. If you register your COM objects, they will be used from the directory where they are registered regardless of what's in the local directory, unless you use reg-free COM or a .local file.
EDIT:
MakeMyManifest is well spoken of as an automatic tool for creating manifests for VB6 projects, haven't tried it myself.
DirectCOM also has fans, again I haven't tried it.
EDIT The MMM website is down. I see here that the author was having trouble with their hosting and has provided another location to get Make My Manifest - download it here.
There is a semi-automatic technique to generate reg-free COM manifests. You can create the manifests with Visual Studio 2008 (you can use a free version like Visual Basic Express Edition). Then make a couple of edits by hand to make the manifests suitable for use from VB6. See this section of this MSDN article for step-by-step instructions - ignore the rest of the article which is about ClickOnce.
It can be sort of confusing because every version of windows, the rules change. Older versions of Windows search the path before the current directory.
A simple solution without manifests:
If your executable file is A.EXE, add a (0-byte, empty) file in the same directory named A.EXE.local -- for older versions of Windows this puts the app directory ahead of the path in the search order.
Found it myself:
Windows does look in the App Directory first:
If SafeDllSearchMode is enabled, the search order is as follows:
The directory from which the application loaded.
The system directory. Use the GetSystemDirectory function to get the path of this directory.
The 16-bit system directory. There is no function that obtains the path of this directory, but it is searched.
The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
The current directory.
The directories that are listed in the PATH environment variable. Note that this does not include the per-application path specified by the App Paths registry key. The App Paths key is not used when computing the DLL search path.
If SafeDllSearchMode is disabled, the search order is as follows:
1. The directory from which the application loaded.
2. The current directory.
3. The system directory. Use the GetSystemDirectory function to get the path of this directory.
4. The 16-bit system directory. There is no function that obtains the path of this directory, but it is searched.
5. The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
6. The directories that are listed in the PATH environment variable. Note that this does not include the per-application path specified by the App Paths registry key. The App Paths key is not used when computing the DLL search path.
according to : http://msdn.microsoft.com/en-us/library/ms682586.aspx
But you can redirect where it looks for .dll's using a Manifest:
http://msdn.microsoft.com/en-us/library/aa375365(VS.85).aspx