CODEWITHSUNDEEP
gccg++
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a-z

Reputation: 1664

What does -lm option do in g++?

What does -lm option do in g++ and when is it needed?

Is there a complete description of g++ options?

Upvotes: 22

Views: 19940

Answers (2)

Evgeni Sergeev
Evgeni Sergeev

Reputation: 23593

The option does nothing for g++: referring to this answer https://stackoverflow.com/a/1033940/1143274 libstdc++ requires libm, so it will always be linked by g++.

However, there is also some sort of an automatic linking behaviour for gcc, investigated on this thread http://www.linuxforums.org/forum/programming-scripting/125526-c-gcc-math-h-lm.html which I can't seem to find an answer as to where that comes from and which libraries it applies to...

Upvotes: 13

Mat
Mat

Reputation: 206727

That's a linker option. It tells the linker to link with (-l) the m library (libm.so/dll). That's the math library. You often need it if you #include <math.h>.

Upvotes: 28

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