https://stackoverflow.com › questions › 5559250

You'll need to specify both files, something like: gcc testpoint.c point.c. ...so that it knows to link the functions from both together. With the code as it's written right now, however, you'll then run into the opposite problem: multiple definitions of main.

https://stackoverflow.com › questions › 61550884

This basically tells the compiler 'assume these functions exist, and I'll make sure you get them when it comes time to compile the executable'. I don't know where these functions came from or what they're for, but you have to pass the object file that contains them to the linker. edited May 1, 2020 at 21:50.

https://www.geeksforgeeks.org › fix-undefined-reference-error-in-cpp

We encounter the ‘undefined reference’ error in C++ mostly due to issues with function or variable definitions, improper linking, or scope/naming problems. By careful checking the code and build process for these common issues, we can successfully resolve this error.

https://thelinuxcode.com › undefined-reference-function-c

An undefined reference error occurs when you call a function that is declared but not defined anywhere accessible to the compiler. Since the function body is missing, the compiler raises this error when linking the object files together into an executable.

https://askubuntu.com › questions › 977858

Although you could link the standard library manually i.e. gcc -o hello hello.cpp -lstdc++, it's not generally done like that. Instead, you should use g++ in place of gcc , which links libstdc++ automatically.

https://techoverflow.net › 2021 › 04 › 11 › how-to-fix-gcc-undefined-reference-to-_finite-or...

/usr/bin/ld: mymath.c:(.text+0x1057): undefined reference to `_finite' and your code won’t compile. Solution: _finite is a function that is only available on Windows. In order to use it on Linux using GCC or G++, one option is to use isfinite() from math.h:

https://stackoverflow.com › questions › 22426574

Running 'gcc -I$HOME/ffmpeg/include program.c -L$HOME/ffmpeg/lib -lavcodec' gives 6 undefined reference errors. Some of the methods are from libavcodec and the others are from libavutil. So I added -lavutil at the end of the command and it compiled.

https://riptutorial.com › c › example › 12342 › undefined-reference-errors-when-linking

One of the most common errors in compilation happens during the linking stage. The error looks similar to this: $ gcc undefined_reference.c. /tmp/ccoXhwF0.o: In function `main': undefined_reference.c:(.text+0x15): undefined reference to `foo'. collect2: error: ld returned 1 exit status.

https://unix.stackexchange.com › questions › 216836

The libraries being linked to should be specified after there is a reference to them. Thus, you will change the command to: gcc -g -O2 -fopenmp -L/usr/lib -o lenstool_tab e_nfwg.o lenstool_tab.o midpnt.o nrutil.o polint.o qromo.o read_bin.o lenstool_tab.o -lcfitsio -lm. This should fix your problem.

https://visualgdb.com › tutorials › linux › libraries › diagnosing

Fixing the ‘Undefined Reference’ Errors for C/C++ Projects. November 15, 2019 libraries, linux, symbols, troubleshooting, undefined reference. This tutorial shows how to various problems related to missing symbols in C/C++ projects.