Loading DLL with dependencies in Inno Setup fails in uninstaller with "Cannot import DLL", but works in the installer

Question

When I uninstall the program I get this error:

Cannot import dll: <utf8>c:\TestProg\IsStart.dll

What have I done wrong here? Can anybody help me to solve this problem?

CheckO4TaskMngrSvcStopAndUninstall stops and deletes the O4TaskManager Service:

Here's the code:

[Files]
Source: "IsStartServer.dll"; DestDir: "{tmp}"; DestName: IsStart.dll
Source: "IsStartServer.dll"; DestDir: "{app}"; DestName: IsStart.dll
Source: "sqlite3x86.dll"; DestDir: "{src}"; DestName: sqlite3.dll
Source: "sqlite3x86.dll"; DestDir: "{app}"; DestName: sqlite3.dll
Source: "sqlite3x64.dll"; DestDir: "{app}"

[Code]
function TaskMngrInst: LongBool;                                                
external 'CheckO4TaskMngrSvcStopAndUninstall@files:IsStart.dll,sqlite3.dll stdcall loadwithalteredsearchpath setuponly';

function TaskMngrUninst: LongBool;                                                
external 'CheckO4TaskMngrSvcStopAndUninstall@{app}\IsStart.dll stdcall uninstallonly';

procedure CurStepChanged(CurStep: TSetupStep);
begin
  if CurStep = ssInstall then
    begin
      TaskMngrInst();
    end;
end;

procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
begin
  if CurUninstallStep = usUninstall then
    begin
      TaskMngrUninst();
      DeleteFile(ExpandConstant('{app}\sqlite3.dll'));
      DeleteFile(ExpandConstant('{app}\IsStart.dll'));
      RenameFile('{app}\sqlite3x64.dll)', '{app}\sqlite3.dll');
    end;
end;

Answer 1

I believe there was series of different problems (some of which were indeed based on my wrong suggestions).

The correct code is, imo:

[Files]
Source: "IsStartServer.dll"; DestDir: "{app}"; DestName: IsStart.dll
Source: "sqlite3x86.dll"; DestDir: "{app}"; DestName: sqlite3.dll

[Code]
function TaskMngrInst: LongBool;                                                
  external 'CheckO4TaskMngrSvcStopAndUninstall@files:IsStart.dll,sqlite3.dll stdcall loadwithalteredsearchpath setuponly';

function TaskMngrUninst: LongBool;                                                
  external 'CheckO4TaskMngrSvcStopAndUninstall@{app}\IsStart.dll stdcall loadwithalteredsearchpath uninstallonly';

The key points:

• Your original problem was the lack of loadwithalteredsearchpath flag in the import declaration for the uninstaller. You need it to load the dependencies (sqlite3.dll).
• You need to install the dependencies (sqlite3.dll) to the {app} for the use by the uninstaller.
• The installed copy of the dependency has to match the name the primary DLL looks for (sqlite3.dll, not sqlite3x86.dll).
• The name of the DLLs in the external declaration has to match the destination filename (DestName: IsStart.dll, DestName: sqlite3.dll), not the original one.
• The dependency must and can be listed in the declaration only when loading the DLLs from within the installer (with the files: prefix). Not when loading the DLL from a physical path ({app}\IsStart.dll). The sole purpose for listing the dependency is for the installer to extract it (it does not load it, the primary DLL does, hence the the previous point). You do not need to list it, when loading physical files, as all files are (must be) installed already. If you use {app}\primary.dll,{app}\dependency.dll, the uninstaller will actually try to load a file with a name {app}\primary.dll,{app}\dependency.dll – obviously failing.
• There's no point installing anything to {tmp} nor {src}.