How to make use others' C library installed not for the system-wide (Ubuntu/Linux)?
I have downloaded and installed a library called htslib for specific bioinformatic use but not for the system (I'm usingUbuntu 18.04). Only parts of the library is needed for my exercise to parse data in a type called VCF format (basically tab-delimited file but contains many information in columns).
My test code (vcf_parser01.c) is attached to make use the VCF API from the htslib, for which the vcf part seems to be what I need and the vcf.h/vcf.c files are also attached here. Maybe the whole htslib is needed, that's one of the parts I need to confirm.
The htslib was compiled and installed locally without error through Makefile with the package, and the structure of the resulted folder is like:
3) To compile my test code, I used:
4) There are many errors believed to the linker related such as:
There were totally 196 "undefined reference to" lines for 39 functions, which seems involving other libraries!
My question is:
How to debug this linker problem?
I think I understand the .o .so .a files, and the -I/-L options for gcc but not in full good catch.
A bigger picture in my mind is to learn how to make use of any non-standard C libraries from others, especially when documentation of the API is not very clear. I narrow down the topic in ANSI/GNU C in Linux platform only.
I may need a full course on this, but I know there are C experts in the forum. Really appreciate anybody could help me out.
Second, you should confirm that these objects are in the PATH, exactly, and that you have read / access permission for them.
Sometimes, even the best sys admins install code under one userid, then they work as another userid, and they do not have permissions to access the file. Happens all the time (at least to me, LOL).
This is generally the first two steps I always take (back to basics, before back to the future).
Insure your PATH(s) are correct and objects / symbols are in the PATH(s), correctly.
Check file and directly permissions for the userid you are using to build.
UNIX and Linux are funny things, they generally do what they are told to do and report back the "facts" as they find them. In your case, gcc cannot find required symbols and objects. This is generally because they cannot find them, i.e. not in the search PATH or the file/directory permissions are "not as required".
Please post back and let me know if you are certain your PATHs are correct and why, using the FULL PATH names to files and directories in your command line for gcc.
Since we are not "standing behind you, watching you type", we cannot "see" what directory you are in, so to be sure, it is always best to use FULL PATH names when troubleshooting a problem like this.
Undefined references means the compiler can't find compiled code for functions being called. If you want to use a subset of the library then you'll have to compile and link all the files used by the code you do want.
In otherwords - if you want to use method a in file a.c and it uses method b in b.c and it uses method c in c.c then you'll need to compile and link a.c, b.c and c,c. I you have an archive file you can link directly to it and the library won't be dynamically loaded at runtime. if you only have a shared library then you, if you are on a Linux system you can investigate rpath as a means to tell the linker where the library is to be found.
The htslib-1.10.2.tar.bz2 is what I downloaded from the website, and the library was compiled from the pkg according to their Makefile.
By the way I tried -L option instead of -I for the gcc command line gave the same error.
The complete actual log file is attached here too for your reference.
Thank you very much again!
You can compile and link using compiler options. The library is referenced using -l<its_name_here> and the path to the library using -L/path/to/lib.
-I is for the path to include directories.
However, if the library isn't in a directory in the linkers path when you run the executable you'll get an error. One way to solve this is to use rpath option.
Note: I'm guessing what you need and what each item is. -I should be used with the path to header -l prepended to the library name and -L preceding the path to the library.
Does the -L option ensure the sub-directories are searched recursively?
The -lhtslib-1.10.2 option of your command line may be wrong in this case as htslib-1.10.2 is a folder under which there are several sub-folders and many *.c *.h *.o *.pico files, but I understand your point. Two files: libhts.so and libhts.a may be the ones I need(permission is checked to be correct). So I tried:
Code:
$ gcc -Wall -O3 -o vcf_parser01 vcf.c vcf_parser01.c -Wl,-rpath,/home/yifangt/Study/C/VCF -L/home/yifangt/Study/C/VCF/htslib-1.10.2 -lhts
/tmp/ccSYd2K4.o: In function `bcf_hdr_set_idx.isra.10':
vcf.c:(.text+0x11d5): undefined reference to `hts_resize_array_'
/tmp/ccSYd2K4.o: In function `vcf_hdr_read':
vcf.c:(.text+0x66ad): undefined reference to `tbx_index_load3'
/tmp/ccSYd2K4.o: In function `vcf_write':
vcf.c:(.text+0xd57a): undefined reference to `hts_idx_tbi_name'
/tmp/ccSYd2K4.o: In function `bcf_index_load3':
vcf.c:(.text+0xdd55): undefined reference to `hts_idx_load3'
/tmp/ccSYd2K4.o: In function `bcf_idx_save':
vcf.c:(.text+0xe181): undefined reference to `sam_idx_save'
collect2: error: ld returned 1 exit status
Under the htslib-1.10.2folder, there are three sub folders cram/, htslib/ and m4/ that may be involved.
In htslib/ sub-folder, *.h files only, so that's for the headers;
In cram/ and m4/ sub-folders, there are *.c, *.h and *.o files (and some other types, which seems for portability, and may not be needed, very likely to me!);
Also I have tried archive the *.o files into library in the format as mylibx.a or mylibx.so files, the error stayed the same. I have attached the link to download the library and my src code. Could it be possible for you to download the library to have a look at the code? That may be easier than what I explained.
Thanks a lot.
Last edited by yifangt; 01-15-2020 at 04:08 PM..
Reason: Add high lighter, correct typos
Does the -L option ensure the sub-directories are searched recursively?
No. Each folder requires a -L entry.
Quote:
Originally Posted by yifangt
The -lhtslib-1.10.2 option of your command line may be wrong in this case as htslib-1.10.2 is a folder under which there are several sub-folders and many *.c *.h *.o *.pico files, but I understand your point. Two files: libhts.so and libhts.a may be the ones I need(permission is checked to be correct). So I tried:
I presumed htslib-1.10-2 was your library. The -l option is for the library itself. If the library is libhts.so then use -lhts
Quote:
Originally Posted by yifangt
Could it be possible for you to download the library to have a look at the code? That may be easier than what I explained.
Thanks a lot.
I'll have a look.
--- Post updated at 09:38 PM ---
Ok. I didn't see a link but grabbed it from github.
If you use the archive its simplest. I'm going to call the root path of the directory where you build the library LIBROOT. You should replace this with the actual path.
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