Question

I’ve installed the GD package (http://hackage.haskell.org/package/gd-3000.4.0) using cabal. When I try to compile the program which uses GD I receive an error:

[mp262554@students:~/jpp/haskell]$ ghc gd.hs
compilation IS NOT required
gd.o: In function `sV8_info':
(.text+0x1bf): undefined reference to `gdzm3000zi4zi0_GraphicsziGD_saveJpegFile_closure'
gd.o: In function `sUY_info':
(.text+0x3be): undefined reference to `gdzm3000zi4zi0_GraphicsziGD_drawLine_closure'
gd.o: In function `sUI_info':
(.text+0x51a): undefined reference to `gdzm3000zi4zi0_GraphicsziGD_newImage_closure'
gd.o: In function `sUI_info':
(.text+0x6a5): undefined reference to `__stginit_gdzm3000zi4zi0_GraphicsziGD_'
gd.o: In function `sVc_srt':
(.data+0x34): undefined reference to `gdzm3000zi4zi0_GraphicsziGD_drawLine_closure'
gd.o: In function `sVc_srt':
(.data+0x38): undefined reference to `gdzm3000zi4zi0_GraphicsziGD_saveJpegFile_closure'
gd.o: In function `sUI_srt':
(.data+0x4c): undefined reference to `gdzm3000zi4zi0_GraphicsziGD_newImage_closure'
collect2: ld returned 1 exit status

Answer 1

GD package provides bindings to GD library written in C. You need to link the C library to your program. Try --make option of the GHC first:

 ghc --make gd.hs

GHC with --make should figure dependencies automatically and link a multi-module program correctly. You can also consider using -l and -L options manually.