finding undefined symbol

Question

I am trying to run a program whose source I downloaded and compiled. When I try to run the program I keep getting the message:

unable to load undefined symbol _z15InvalidateImageSs

I am trying to determine why I am getting this error. The program is actually a library that is loaded by another program. My program compiles to a .so file.

I ran:

$ nm myprog.so > nm.txt

the symbol shows up in the file, but has no address associated with it.

I searched the source tree for the symbol using:

$ find . -type f | xargs fgrep -I '_zinvalidateimagess' | grep -v 'Binary

I got no results. 2. I searched all standard load libraries for the symbol:

$ scanelf -l -s _zInvalidateImageSs | grep -I '_zinvalidateImageSs'

no results again.

So my question is: If the symbol is never referenced anywhere in the source tree, why is it a problem in the .so file? How do I figure out where this symbol is supposed to be coming from?

Search for InvalidateImage .The other characters are due to C++ name mangling. — Mark Plotnick, Mar 31 '15 at 08:05
What does ldd program show? Paste the results into your question, please. — Faheem Mitha, Mar 31 '15 at 08:10

score 2 · Answer 1 · edited May 23 '17 at 12:40

The source for the library can declare a symbol without defining it, by doing something like this

extern InvalidateImage(const char *);

and later using it

const char *foo = InvalidateImage(bar);

Because it is a library, you would not notice this until you attempt to run the program which uses this symbol. The place to look for the symbol is where you downloaded the library's source: likely the developer of that library provides either the related source directly or some clues regarding where they get it from.

For what it's worth, I use scripts (exports and externs) to check for missing symbols in the programs which I maintain.

finding undefined symbol

1 Answers1