Issue with api_GetModuleFileName Windows API func

Blitz3D Forums/Blitz3D Programming/Issue with api_GetModuleFileName Windows API func

Zethrax (Posted 2015) [#1]

So, what am I bollixing up here? Basically I'm trying to use the Kernel32.dll function GetModuleFileNameA via the kernel32.decls found at: http://www.blitzbasic.com/codearcs/codearcs.php?code=1180 The point of my GetAppName$() function is to get the executable filename of the Blitz3D program. I'm having a couple of problems with this though. Problem 1: While the 'size' value returned by 'api_GetModuleFileName' is non-zero (which should indicate that no errors were encountered), the string returned contains all zero values. Problem 2: If I compile this code as an executable and run it I get a MAV followed by a hard crash. This happens in both debug and non-debug mode. This problem seems to be caused by the call to 'api_GetModuleFileName' (commenting out that call eliminates the problem), but the crash doesn't happen immediately after that call. The program will usually run the 'While' loop a few times before the crash occurs. I've tried setting a larger than required buffer and string size for 'api_GetModuleFileName' to return the filepath string in, but that doesn't stop the problems. I've tried using SystemProperty( "AppHWND" ) as the first parameter to use the app handle rather than the Null that signals the function to return the filename of the calling app. That results in size = 0, which is probably a permission issue. The definition for 'api_GetModuleFileName' in the 'kernel32.decls' decls file seems to be using a string for 'lpFileName$' when it should possibly be using an integer so that a pointer value can be sent. Changing this to an int results in a mav when doing a quickie compile and run though. This isn't a huge problem for the project I'm working on as I can simply hard code the filename of the app rather than using 'api_GetModuleFileName' to derive it. I'm curious about what's gone pear shaped here though. ; REQUIRES:- ; - Userlib 'kernel32.decls' decls file for 'Kernel32.dll' - http://www.blitzbasic.com/codearcs/codearcs.php?code=1180 ; REFERENCES:- ; - https://msdn.microsoft.com/en-us/library/ms683197(VS.85).aspx ; - http://stackoverflow.com/questions/4000877/how-can-i-get-the-current-instances-executable-file-name-from-native-win32-c Function GetAppName$() ; Gets the filename of the Blitz program, including the file extension. ; REQUIRES:- ; - Userlib 'kernel32.decls' decls file for 'Kernel32.dll' - <a href="http://www.blitzbasic.com/codearcs/codearcs.php?code=1180" target="_blank">http://www.blitzbasic.com/codearcs/codearcs.php?code=1180</a> ; NOTES:- ; The Windows API function 'GetModuleFileNameA' that 'api_GetModuleFileName' references is part of 'Kernel32.dll'. ; The returned characters should all be ascii as that's what the Blitz3D application uses and 'GetModuleFileName' supposedly takes that fact into account. ; The path character limit on Windows is 260 characters (MAX_PATH) including headers and the terminating null character. Other limits can potentially exist but the core Windows API apparently sticks to the 260 char limit by default for backwards compatibility reasons. ; REFERENCES:- ; - <a href="https://msdn.microsoft.com/en-us/library/ms683197(VS.85).aspx" target="_blank">https://msdn.microsoft.com/en-us/library/ms683197(VS.85).aspx</a> ; - <a href="http://stackoverflow.com/questions/4000877/how-can-i-get-the-current-instances-executable-file-name-from-native-win32-c" target="_blank">http://stackoverflow.com/questions/4000877/how-can-i-get-the-current-instances-executable-file-name-from-native-win32-c</a> bank_size = 1000 ; *** Note that I'm using plus-sized buffer and string parameters below in an attempt to get compiled executables from pooping the bed. bank = CreateBank( 3000 ) ; We'll use 1000 chars just to be on the safe side. size = api_GetModuleFileName( 0, bank, 1000 ) ; Get the filepath and put it in the bank. Returns the size of the string stored in the bank, not including the terminating null character. ;size = api_GetModuleFileName( SystemProperty( "AppHWND" ), bank, 1000 ) ; *** The 'api_GetModuleFileName' seems to be causing the MAV followed by the hard crash. Print "Size: " + size If ( size > 0 ) And ( size <= bank_size ) offset = size - 1 While offset > -1 b = PeekByte( bank, offset ) Print "Offset: " + offset + " | Byte: " + b ; *** Debug *** If b = 92 Then Exit ; If the character peeked was a backslash then we've found all the filename characters. filename$ = Chr( b ) + filename$ offset = offset - 1 Wend EndIf FreeBank bank Return filename$ End Function Graphics 400, 800, 0, 2 Print GetAppName$() WaitKey End

Jimmy (Posted 2015) [#2]

Donīt have a computer to try the code on, does the Window API do something special? Otherwise I would suggest try using Videz & Rross code GetExeName$ ( http://www.blitzbasic.com/codearcs/codearcs.php?code=3177 ) this does the trick equally well I think and It has never failed me, seems rockksolid.

Guy Fawkes (Posted 2015) [#3]

http://www.blitzbasic.com/codearcs/codearcs.php?code=3177 *

Zethrax (Posted 2015) [#4]

Sending a string as the middle parameter for api_GetModuleFileName seems to eliminate the mav and crash issues, but I still end up with an unmodified string. I ended up writing this code as a substitute. I works fine, but that 'GetCommandLine' in the posted code archive link looks interesting, so thanks for that. ; -- Find the filename of the program executable and place it in 'value$', or set 'value$' as an empty string if not found. ; (Note that the application's executable file needs to be the only file with an ".exe" extension in the application folder. Put any other ".exe" files (tools, etc) in a sub-folder.) value$ = "" ; Initialize 'value$'. This line won't be necessary if 'value$' wasn't previously set to a value. value$ = SystemProperty( "appdir" ) ; Get the filepath of the application folder. dir = ReadDir( value$ ) ; Open the application folder to read the contents. If dir ; If the folder was opened successfully... Repeat value$ = NextFile$( dir ) ; Grab the filename of a file in the folder (this could also potentially be the name of a sub-folder)... If value$ = "" Then Exit ; If we've reached the end of the folder contents then exit the loop. This will result in 'value$' being set to null. If Len( value$ ) > 5 ; If it has enough characters for the ".exe" extension plus at least one for the name... If Right( value$, 4 ) = ".exe" ; If it ends with the ".exe" extension. If FileType( value$ ) = 1 ; If it exists and it's a file and not a folder (which can also potentially be named with an ".exe" at the end, though unlikely)... Exit ; We've found the filename of the executable and stored it in 'value$', so exit the loop. EndIf EndIf EndIf Forever CloseDir dir ; Close the folder. EndIf ;------ EDIT: I ended up going with the code below, which is based on the 'GetCommandLine' Windows API function. This gets the absolute path of the executable enclosed in quote marks, which works for what I'm trying to achieve. Function GetAppFilepath$() ; Gets and returns the absolute filepath of the Blitz program executable enclosed in quotes. ; Note that 'api_GetCommandLine' appears to reliably return the filepath of the executable enclosed in quote marks. ; REQUIRES:- ; - Userlib 'kernel32.decls' decls file for 'Kernel32.dll' - <a href="http://www.blitzbasic.com/codearcs/codearcs.php?code=1180" target="_blank">http://www.blitzbasic.com/codearcs/codearcs.php?code=1180</a> value$ = api_GetCommandLine() Print value$ If Len( value$ ) < 3 Then Return "" ; If there's not at least two characters in there for some reason then our code could have problems, so return with an empty string. s = Instr( value$, Chr( 34 ), 1 ) l = ( Instr( value$, Chr( 34 ), s + 1 ) - s ) + 1 Return Mid( value$, s, l ) End Function