undefined reference to `sqrt'

Question

Part of my program is to calculate sqrt of float number. When I write sqrt(1.0f); I success to compile the program,but when I write sqrt(-1.0f); the compilation fails with undefined reference to 'sqrt' - I suppose that in this case the nan value will be returned... I compile the program uing gcc. When I compile it with visual studio it is compiled successfuly with negative argument to sqrt. How the problem could be solved Thank you

gcc myprog.c -o myprog -lm the -l to include a library m for the math library -lm. — old_timer, Jan 08 '12 at 19:41

score 5 · Accepted Answer · answered Jan 08 '12 at 19:44

You have to add the -lm flag on most Unix-based systems, as in:

Compile using:

gcc -c file.c

and then link using:

gcc -o program file.o -lm

Or if you don't want to separate the two compilation steps, simply write:

gcc -o program file.c -lm

score 4 · Answer 2 · answered Jan 08 '12 at 19:41

4

Link with -lm to link with the math library

answered Jan 08 '12 at 19:41

Manuel Selva

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Can you please give a reason for it. I tried including in headers, but then facing the error as mentioned in the question. – Akash Chandwani Nov 27 '16 at 18:06

undefined reference to `sqrt'

2 Answers2

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