List of variables defined in the code (c++)

Question

Does someone know if in C++ is there a function to get the name of all the variables defined in a code?

Example code:

int main() { double Var1; double Var2; UnknownFunction(); }

In this case the function I'm searching for(UnknownFunction) should output a vector of strings containing "Var1" and "Var2".

Thank you in advance.

Why do you want to do this? And will all of the variables you're interested in be of the same type (double here)? — scohe001
– scohe001, Commented Dec 24, 2019 at 16:06
What are you really trying to do? Why do you think you need this? — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Dec 24, 2019 at 16:07
There is no way to do that. If you tell us more about what you're trying to do, we might be able to suggest a different solution. — HolyBlackCat
– HolyBlackCat, Commented Dec 24, 2019 at 16:07
What you're looking for is called reflection, and C++ doesn't support this. Some scripting languages like Python and Javascript do. Instead, you make your own symbol table, and have a map of strings to values. Your formula solver can use the symbol names to get and set values in the table. — parktomatomi
– parktomatomi, Commented Dec 24, 2019 at 16:13
@FGP92 You have asked an X-Y question. The thing you really want to do is in your last comment - you'd do better to ask that question. Do you really mean "equation solver" or more simply an "expression evaluator"? I say more simply - it is still not that simple. What you need is a string to value look-up or hash table, the variables declared in your C code are irrelevant to the variables used in your expression evaluator. — Clifford
– Clifford, Commented Dec 24, 2019 at 16:17

Clifford · Accepted Answer · 2019-12-24 16:27:12Z

5

When C++ code has been compiled to machine code, the symbol names are resolved to explicit memory addresses by the compile/link process and are not available to the program at run time, so the question makes no real sense.

Symbolic information is retained for use in a debugger and a debugger can present all variables in scope.

edited Dec 24, 2019 at 16:27

answered Dec 24, 2019 at 16:11

Clifford

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8 Comments

Lightness Races in Orbit Over a year ago

The question is about C++. Also there's no such thing as "a compiled language".

Clifford Over a year ago

@LightnessRacesBY-SA3.0 Corrected C++. Not sure what your point about "compiled language" is - perhaps a little pedantic? The term serves my purpose for this discussion - in the sense that the compiler generates machine code where variable names are not retained.

Joel Trauger Over a year ago

@LightnessRacesBY-SA3.0 Show me a C interpreter that's not an online "compiler"

Clifford Over a year ago

@LightnessRacesBY-SA3.0 : Nonetheless your objection has led me to modify the text for a perhaps clearer and as a side-effect hopefully less objectionable text.

FGP92 Over a year ago

Thank you very much for the answers. I already thought to create a vector of objects "variabile" each containing name and value and then creating a map that links the name to the corresponding value. Thank you for your suggestions.

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