I kind of recall that in Turbo Pascal or early Delphi versions there were options to make functions calling convention not register by default but any other type.
Maybe i mistake it for {$W+} or {$STACKFRAMES ON} option, which affects functions prologue and epilogue as well.
I do not want to use pascal pre-processors, but if i could change default convention for some unit it could be useful to me.
Free Pascal has the $calling directive:
http://www.freepascal.org/docs-html/prog/progsu7.html#x13-120001.1.7
It's typically used to fix old units that have assembler routines with assumptions
about calling convention built in to them.
It cannot be done. The default calling convention cannot be modified by compiler options.
Related
My delphi application runs scripts using JvInterpreter (from the Jedi project).
A feature I use is runtime evaluation of expressions.
Script Example:
[...]
ShowMessage(X_SomeName);
[...]
JvInterpreter doesn't know X_SomeName.
When X_SomeName's value is required the scripter calls its OnGetValue-callback.
This points to a function I handle. There I lookup X_SomeName's value and return it.
Then JvInterpreter calls ShowMessage with the value I provided.
Now I consider switching to DelphiWebScript since it has a proper debug-interface and should also be faster than JvInterpreter.
Problem: I didn't find any obvious way to implement what JvInterpreter does with its OnGetValue/OnSetValue functions, though.
X_SomeName should be considered (and actually is, most of the time) a variable which is handled by the host application.
Any Ideas?
Thanks!
You can do that through the language extension mechanism, which has a FindUnknownName method that allows to register symbols on the spot.
It is used in the asm lib module demo, and you can also check the new "AutoExternalValues" test case in ULanguageExtensionTests, which should be closer to what you're after.
I am looking for a predefined symbol to write a code like that:
{$IFDEF LAZARUS}
// code compiles by fpc/lazarus
{$ELSE}
// code compiles by delphi
{$ENDIF}
Use FPC
{$IFDEF FPC}
For GUI applications afaik the "LCL" symbol is defined inside Lazarus projects. In this case it probably won't matter.
In general, for bigger codebases, I would avoid having too much ifdef FPC/LCL and ifdef in your sourcecode though. It makes adding an exception or other version harder.
Use a system like JCL and Zeos(7) are using, where you give most differences an own name (like "USE_FPCUNIT" or "USE_DUNIT") and link these to versions in a central includefile.
For a short treatise on the subject see http://www.stack.nl/~marcov/porting.pdf (chapter 2)
P.s. I would consider Pocketstudio, TP,GPC,VP and WDSybil (and whatever I forgot) dead for most practical purposes and the bytecode variants Canterbury Pascal/Component Pascal/Oxygene/Prism/Delphi.NET incompatible (most are more Oberon than Pascal anyway). That pretty much leaves Delphi, Kylix and FPC to worry about.
When I use Delphi directives in code, like:
{$IFDEF something}
.
.
.
{$ENDIF}
Where do I assign the word 'something' in the project? I tried in some places in project options but it didn't work. Guess I didn't find the correct one.
It's in the Conditional Defines slot under Project | Options, which looks like this on D2010:
Other answers have pointed you at the places to define symbols and the scope implications of the different approaches.
However, what no-one has yet mentioned is that if you change the DEFINE symbols you MUST do a FULL BUILD of your project for them to have any effect on your code.
When you "Compile" the Delphi compiler will only compile units which have themselves changed since the previous compile. If you change DEFINE symbols this doesn't change any project units, so if the units are not re-compiled then the change in DEFINE symbols will not have ANY effect in those units.
To FORCE changes in DEFINE symbols to be applied in ALL units, you MUST "build", not compile.
This may explain why your attempt to set defines did not appear to work previously
You can also define them in {$DEFINE <symbol>} directives. What changes is the scope. When you define a <symbol> under conditional defines in the project options, the scope is global to the whole project. $DEFINE directives are valid only from the point they are declared to the end of the current module, or until an $UNDEF directive using the same <symbol> is encountered. What to use depends on your needs, and what the IFDEF does.
There are two places where you can put conditional defines that are used in all units of a project:
in the project options (as David Heffernan already said)
in an include file that is included in all of these units
Why do I mention the second option? Because it allows specialized processing based on the VERxxx conditional define and other conditional defines given in 1. See jedi.inc (from the Jedi JCL) for an example.
Also, as Deltics said: When it determines which units to recompile, the compiler only checks whether the unit itself has changed, not whether the conditional defines or any include files have changed. So if you change conditional defines, you must do a rebuild, not just a recompile. Since the Delphi compiler is very fast, this fortunately does not make much of a difference for compile times.
You can define global symbols in external file with .inc extension.
Create a new text file, put in it all you defines and save it as for instance Predefines.inc:
--- Content of the file Predefines.inc ---
{$DEFINE Symbol}
{$IFDEF Symbol}
{$DEFINE AnotherSymbol}
{$ENDIF}
In you Delphi modules, where you need to check are symbols defined, put this code in interface section:
interface
{$I Predefines.inc}
uses ...
// Check you defines
{$IFDEF Symbol}
...
{$ENDIF}
We have some ancient Delphi code (might have even originated as Turbo Pascal code) that uses {$I-}, aka {$IOCHECKS
OFF}, which makes the code use IOResult instead of exceptions for disk I/O errors.
I want to get rid of the {$I-} and bring this code forward into the 1990s, but to do that, I'd like to know what all is affected by {$IOCHECKS OFF}. Does this only affect the crufty old built-in I/O functions like AssignFile / Reset / Rewrite / Append / CloseFile? Or does it affect more modern things like TFileStream as well? More importantly, what else might be affected that I'm not thinking of? (Delphi Basics suggests that it also affects MkDir and RmDir. If it affects those, there have to be more.)
The Delphi 2007 Help topic "Input output checking (Delphi)" (ms-help://borland.bds5/devcommon/compdirsinput_outputchecking_xml.html) says that this affects "I/O procedure[s]", and that "I/O procedures are described in the Delphi Language Guide." This doesn't help much, since CodeGear has never shipped a Language Guide, and the last time Borland shipped one was Delphi 5.
Which functions and classes behave differently under {$I-}?
EDIT: The accepted answer gives some great background, but here's the quick summary in alphabetized list form: {$IOCHECKS OFF} only affects the following routines from the System unit.
Append
BlockRead
BlockWrite
ChDir
CloseFile
Eof
Eoln
Erase
FilePos
FileSize
Flush
MkDir
Read
Readln
Rename
Reset
Rewrite
RmDir
Seek
SeekEof
SeekEoln
SetLineBreakStyle
Truncate
Write
Writeln
Since $I is a compiler directive, it can only affect compiler-generated code, and it can only affect code that actually gets compiled.
For those two reasons, it cannot affect things like TFileStream. It's a class in Classes.pas, which is a unit you don't compile. Any code in it is not affected by the $I directive. Furthermore, the compiler doesn't treat that class specially in any way. It's just another ordinary class.
The $I directive affects the language built-in functions that you've mentioned. The compiler generates calls to those functions specially. It also affects calls to write, writeln, and readln. It should also affect BlockRead and BlockWrite.
You can check the source code. Anything that calls SetInOutRes is susceptible to $I. That includes functions that open files (Append, Reset, and Rewrite), as well as anything else that accepts a parameter of type file or TextFile (Flush, BlockRead, BlockWrite, Erase, FilePos, Seek, FileSize, Read, Readln, Write, Writeln, Rename, Eof, SeekEof, Eoln, SeekEol, Truncate, SetLineBreakStyle, and CloseFile). Also, anything that calls InOutError (ChDir, MkDir, amd RmDir).
Notably absent from the list is AssignFile. That function doesn't actually do any I/O. It just sets up the file record so that Append, Reset, and Rewrite will know what to do.
I should point out that looking at the source code is just inference. The $I directive controls whether the compiler will insert calls to the __IOTest function in your own code after you call certain other functions. That function checks the value of InOutRes, and if it's not zero, it raises a run-time error (which may yield an exception if SysUtils is included in your program). We can't check the source code to directly find out what functions are affected by $I (since it's only called in compiler-generated code), so we're really just looking for which functions set InOutRes, with the assumption that they wouldn't bother doing that if they didn't know the compiler would check for it afterward.
I am writing a unit test infrastructure for a large Delphi code base. I would like to link calls to pure functions in SysUtils.FileExists for example to a "MockSysUtils.FileExists" instead.
Creating a SysUtils unit with the same interface is not appreciated by the compiler.
What I am thinking of is to hook in my mock function at runtime. Is this possible nowadays?
Any other suggestions?
Regards,
Peter
Replacing a function at runtime is difficult but usually technically possible. "All" you need to do is:
take the address of the function in question
disassemble the first 5 bytes or so (to check for a RET instruction - very small routines may abut another routine, preventing you from replacing it)
change its page protection (with VirtualProtect) to be writable
rewrite the first 5 bytes with a JMP rel32 instruction (i.e. E9 <offset-to-your-func>)
implement your version function as normal, making sure it has the same arguments and calling convention as the function you are mocking
An easier approach would be to link against a different version of SysUtils.pas. That will require you to also recompile all the units in the RTL and VCL that depend on SysUtils.pas, but it is likely quite a bit easier than the function intrumentation approach described above.
The easiest approach is the language-level one, where either you don't directly rely on SysUtils at all (and so can switch at a higher level), or you modify the uses declaration to conditionally refer to a different unit.
You can do it with MadCodeHook. Use the HookCode function, give it the address of the function you want to replace and the address of the function you want to be called instead. It will give you back a function pointer that you can use for calling the original and for unhooking afterward. In essence, it implements the middle three steps of Barry's description.
I think MadCodeHook is free for personal use. If you're looking for something freer than that, you can try to find an old version of the Tnt Unicode controls. It used the same hooking technique to inject Unicode support into some of the VCL's code. You'll need an old version because more recent releases aren't free anymore. Find the OverwriteProcedure function in TntSystem.pas, which is also where you'll find examples of how to use it.
Code-hooking is nice because it doesn't require you to recompile the RTL and VCL, and it doesn't involve conditional compilation to control which functions are in scope. You can hook the code from your unit-test setup procedure, and the original code will never know the difference. It will think it's calling the original FileExists function (because it is), but when it gets there, it will immediately jump to your mocked version instead.
You could also just add a unit that only contains the functions you want to mock to the test unit's uses clause. Delphi will always use the function from the unit that is listed last. Unfortunately this would require you to change the unit you want to test.
Your Mock-Sysutils unit:
unit MockSysutils;
interface
function FileExists(...) ...
...
end.
Your unit, you want to test:
unit UnitTotest;
interface
uses
Sysutils,
MockSysUtils;
...
if FileExists(...) then
FileExists will now call the version from MockSysutils rather than from Sysutils.
Thanks,
yes, it would be great to have TSysUtils class for example instead that I could inherit with my MockSysUtils. But, that is not the case and the code base huge. It will be replaced bit by bit, but I wondered if there was a quick-start solution.
The first approach is ok for one function perhaps, but not in this case I guess.
I will go for the second approach.
This is slightly way out there but here is another alternative.
When building your unit tests and your main codebase to go with it, you could grep all the functions you wish to replace and specify the unit to use
Instead of
fileexists(MyFilename);
you could grep fileexists and replace with
MockTests.fileexists(MyFileName);
If you did this at build time (using automated build tools) it could easily be done and would provide you with the greatest flexibility. You could simply have a config file that listed all the functions to be replaced.