How to build third-party libraries in a C++ project?

Question

C++ / C#

Good day.
Of extreme interest is the question of how to properly build third-party libraries using the MSYS and MinGW tools, as well as include the compiled libraries in the code.
Actually, the essence of a particular situation:
There was a need to work with images (increasing contrast and cropping an image), a Google search pointed me to the libgd library, along with which additional modules for working with jpeg,png,tff and so on were downloaded (link to libgd - https://libgd.github.io/ ).
After a VERY long torment, libgd.dll and libgd.a were built by various hooks and crooks.
As far as I understand, libgd.a is a library for MinGW
www.cyberforum.ru/cpp-beginners/thread978847.html :

Libraries for MinGW have extension .a and prefix lib ( ie libsndfile-1.a ).
You either need to download the libraries for MinGW or build them yourself.

Now a question.
There is a simple example, which was taken solely for performance testing:

/* Bring in gd library functions */
#include "src/gd.h"

/* Bring in standard I/O so we can output the PNG to a file */
#include <stdio.h>

int main() {
  /* Declare the image */
  gdImagePtr im;
  /* Declare output files */
  FILE *pngout, *jpegout;
  /* Declare color indexes */
  int black;
  int white;

  /* Allocate the image: 64 pixels across by 64 pixels tall */
  im = gdImageCreate(64, 64);

  /* Allocate the color black (red, green and blue all minimum).
    Since this is the first color in a new image, it will
    be the background color. */
  black = gdImageColorAllocate(im, 0, 0, 0);

  /* Allocate the color white (red, green and blue all maximum). */
  white = gdImageColorAllocate(im, 255, 255, 255);

  /* Draw a line from the upper left to the lower right,
    using white color index. */
  gdImageLine(im, 0, 0, 63, 63, white);

  /* Open a file for writing. "wb" means "write binary", important
    under MSDOS, harmless under Unix. */
  pngout = fopen("test.png", "wb");

  /* Do the same for a JPEG-format file. */
  jpegout = fopen("test.jpg", "wb");

  /* Output the image to the disk file in PNG format. */
  gdImagePng(im, pngout);

  /* Output the same image in JPEG format, using the default
    JPEG quality setting. */
  gdImageJpeg(im, jpegout, -1);

  /* Close the files. */
  fclose(pngout);
  fclose(jpegout);

  /* Destroy the image in memory. */
  gdImageDestroy(im);
}

When I try to compile the source code on the command line, I get the following (blank lines added for readability):

C:\CPPImageCorrecing>g++ CPPImageCorrector.cpp -o CPPImageCorrector.exe

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0x26)
: undefined reference to `[email protected]'

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0x51)
: undefined reference to `[email protected]'

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0x7c)
: undefined reference to `[email protected]'

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0xb6)
: undefined reference to `[email protected]'

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0xfb)
: undefined reference to `[email protected]'

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0x11a
): undefined reference to `[email protected]'

C:\Users\0BD6~1\AppData\Local\Temp\ccy0WVTF.o:CPPImageCorrector.cpp:(.text+0x140
): undefined reference to `[email protected]'
collect2.exe: error: ld returned 1 exit status

A huge request to knowledgeable people, explain what I'm doing wrong?

Answer 1

You didn't tell the linker the path to the library, and he doesn't know where to get method implementations from the gd.h header file