Delphi - Trying to get StackTrace for an exception - delphi

Question

I have an exception logger that logs all exceptions to a log file:
class function TLogger.LogException (ACaller: String; E: Exception): Boolean;
var
LogFilename, tmp: string;
LogFile: TextFile;
appsettings: TApplicationSettings;
begin
// prepare log file
appsettings:=TApplicationSettings.Create;
try
tmp:=appsettings.ErrorLogsLocation;
finally
FreeAndNil(appsettings);
end;
if NOT (DirectoryExists(tmp)) then
CreateDir(tmp);
//We create a new log file for every day to help with file size issues
LogFilename:=IncludeTrailingPathDelimiter (tmp) + 'LJErrors_' + FormatDateTime('yyyy-mm-dd', Now) +'.log';
try
AssignFile (LogFile, LogFilename);
if FileExists (LogFilename) then
Append (LogFile) // open existing file
else
Rewrite (LogFile); // create a new one
// write to the file and show error
Writeln(LogFile, CRLF+CRLF);
Writeln (LogFile, 'Application Path: ' + ExtractFilePath(ParamStr (0)));
Writeln (LogFile, 'Application Version: ' + TUtility.GetAppVersionString);
Writeln (LogFile, 'Operating System: ' + TUtility.GetOSInfo);
Writeln (LogFile, 'Error occurred at: ' + FormatDateTime ('dd-mmm-yyyy hh:nn:ss AM/PM', Now));
Writeln (LogFile, 'Logged By: ' + ACaller);
Writeln (LogFile, 'Unit Name: ' + E.UnitName);
Writeln (LogFile, 'Error Message: ' + E.Message);
Writeln (LogFile, 'Error Class: ' + E.ClassName);
Writeln (LogFile, 'Base Exception Error: ' + E.BaseException.Message);
Writeln (LogFile, 'Base Exception Class: ' + E.BaseException.ClassName);
Writeln (LogFile, 'Stack Trace: ' + E.StackTrace);
Result:=True;
finally
// close the file
CloseFile (LogFile);
end;
end;
To enable the Exception.StackTrace, I am using JCLDebug as outlined in: https://blog.gurock.com/working-with-delphis-new-exception-stacktrace.
unit StackTrace;
interface
uses
SysUtils, Classes, JclDebug;
implementation
function GetExceptionStackInfoProc(P: PExceptionRecord): Pointer;
var
LLines: TStringList;
LText: String;
LResult: PChar;
begin
LLines := TStringList.Create;
try
JclLastExceptStackListToStrings(LLines, True, True, True, True);
LText := LLines.Text;
LResult := StrAlloc(Length(LText));
StrCopy(LResult, PChar(LText));
Result := LResult;
finally
LLines.Free;
end;
end;
function GetStackInfoStringProc(Info: Pointer): string;
begin
Result := string(PChar(Info));
end;
procedure CleanUpStackInfoProc(Info: Pointer);
begin
StrDispose(PChar(Info));
end;
initialization
// Start the Jcl exception tracking and register our Exception
// stack trace provider.
if JclStartExceptionTracking then
begin
Exception.GetExceptionStackInfoProc := GetExceptionStackInfoProc;
Exception.GetStackInfoStringProc := GetStackInfoStringProc;
Exception.CleanUpStackInfoProc := CleanUpStackInfoProc;
end;
finalization
// Stop Jcl exception tracking and unregister our provider.
if JclExceptionTrackingActive then
begin
Exception.GetExceptionStackInfoProc := nil;
Exception.GetStackInfoStringProc := nil;
Exception.CleanUpStackInfoProc := nil;
JclStopExceptionTracking;
end;
end.
I have enabled the following options in Project Options:
Compiling: Debug Information, Local Symbols, Symbol Reference Info, Use debug .dcus, Use imported data references
Linking: Debug Information
However, when I trigger an exception, even though the GetExceptionStackInfoProc gets triggered, the Exception.StackInfo is always an empty string. Any ideas as to what I may be missing?
UPDATE 20170504: Thanks to Stefan Glienke for the solution. For completeness, I am including the code here for the changed GetExceptionStackInfoProc procedure that incorporates his solution:
function GetExceptionStackInfoProc(P: PExceptionRecord): Pointer;
var
LLines: TStringList;
LText: String;
LResult: PChar;
jcl_sil: TJclStackInfoList;
begin
LLines := TStringList.Create;
try
jcl_sil:=TJclStackInfoList.Create(True, 7, p.ExceptAddr, False, nil, nil);
try
jcl_sil.AddToStrings(LLines, true, true, true, true);
finally
FreeAndNil(jcl_sil);
end;
LText := LLines.Text;
LResult := StrAlloc(Length(LText));
StrCopy(LResult, PChar(LText));
Result := LResult;
finally
LLines.Free;
end;
end;

Answer 1

You need to create it yourself (and free it):
TJclStackInfoList.Create(True, 7, p.ExceptAddr, False, nil, nil);
On that instance you can call AddToStrings.
For more info take a look at JclDebug.GetExceptionStackInfo. The value for AIgnoreLevels is taken from there but in my tests I always had one entry too much so I increased it by one.
The following it a snippet from what I get from a Button1 application calling RaiseLastOSError;
[0042BFE5] System.SysUtils.Sysutils.RaiseLastOSError$qqrix20System.UnicodeString (Line 24937, "System.SysUtils.pas")
[0042BF5B] System.SysUtils.Sysutils.RaiseLastOSError$qqrv (Line 24919, "System.SysUtils.pas")
[005CD004] Unit85.TForm85.Button1Click$qqrp14System.TObject (Line 28, "Unit85.pas")
[0051D567] Vcl.Controls.TControl.Click$qqrv (Line 7429, "Vcl.Controls.pas")
[00534CDA] Vcl.StdCtrls.Stdctrls.TCustomButton.Click$qqrv (Line 5434, "Vcl.StdCtrls.pas")

Answer 2

If you actually read the JclDebug unit, you will see that initialization and finalization sections have registration and deregistration code, so simply placing the unit into the uses section is enough. (See SetupExceptionProcs)