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# Automatic code insertion with VC++

## 7 posts in this topic

Is there any to get Visual C++ 2003 to automatically insert a piece of code at the start of every function? Ideally this would happen before the preprocessor runs and will not make any changes to the code files (much like macro replacement) and could be enabled/disabled per build configuration.
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If I understand what you are asking, then no. Why not just use a macro?
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In MSDevStudio you can use the /Gh option to insert a call to _penter at the start of every function. You can also do /GH to add a call to _pexit at the end of every function. Look up the references for the compiler options for more info.

Skizz
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I didn't want to use a macro because that would require me to explicitly call the macro at the start of every function.

_penter and _pexit won't work either, because I'm trying to access the __FILE__, __FUNCTION__ and __LINE__ macros at the start of every function.

What I'm really want to do is this:

class FuncTracker{public:  FuncTracker(const std::string& name):_name(name)  {      f << "entering: " << _name <<std::endl;  }  ~FuncTracker()  {     f << "leaving: " << _name <<std::endl;  }  std::string _name;static file f;}

Then in every function:

void f(){   FuncTracker _funcTracker;//I want this line to be inserted in every function}

Obviouslyonce this is working it can be expanded to do useful work.
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Ah, that's not so easy. It's doable using the _penter/_pexit methods - you will need to get the function address (in EIP register) and compare it against addresses in the map file that can be generated by the linker (assuming no rebasing has occurred). It'll be very slow though.

The only other way is to use macros. You can make this a bit easier on yourself and more robust by using the following:
class ExecutionTracker{private:    ExecutionTracker(void);public:    ExecutionTracker(char *function, char *file, int line) :        m_func (function),        m_file (file),        m_line (line)    {        cout << "Entering " << m_func << ", " << m_file << ":" << m_line << endl;    }    ~ExecutionTracker (void)    {        cout << "Exiting " << m_func << ", " << m_file << ":" << m_line << endl;    }private:    char        *m_func,        *m_file;    int        m_line;};#define TRACKER ExecutionTracker track (__FUNCTION__, __FILE__, __LINE__);void main (int argc, char *argv []){    TRACKER;    // code....}

which only requires one macro per function and neatly copes with multiple exits.

Skizz

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This has been bugging me for awhile as well.

It has to be possible, even if it requires some elementary source pre-processing before being compiled by cl.exe. It is irritating that this capability is such a pain in the ass to orchestrate, because both of the pieces of the puzzle are sitting right in front of us: the __FUNCTION__ macro, and _penter/_pexit. However, the two just don't work with one another unless we want to annotate each and every function with ugly macros.

The question becomes: how difficult would it be to correctly parse out the beginning of a C++ function from a source file? If it isn't terrible, then injection becomes trivial.
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It's exactly what _penter and _pexit are for. You won't be able to use any user-friendly macros, but you will be able to examine the stack, and figure out the function and file and line number from the debugging information.
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It annoys me that any sort of readable diagnostics can only come after the fact.
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