link-system-library.md

How do I link a system library like -lm, -ldl, or advapi32.lib?

My project requires linking -lm and I tried importing libm%lib{m} but then I get strange errors like there not being a static variant available.

System libraries like -lm and -ldl (which are essentially extensions of libc) or Windows Platform SDK libraries like advapi32.lib and ws2_32.lib should not be imported. Instead, you should list them in the *.libs variables (c.libs, cxx.libs, or cc.libs). For example:

if ($c.target.class != 'windows')
  c.libs += -lm

Or:

if ($cxx.target.class == 'windows')
{
  if ($cxx.target.system == 'mingw32')
    cxx.libs += -ladvapi32
  else
    cxx.libs += advapi32.lib
}

If a system library is an interface dependency of your library (see Library Exportation and Versioning for background), then it should also be listed in *.export.libs, for example:

if ($c.target.class != 'windows')
{
  c.libs += -lm
  lib{hello}: c.export.libs = -lm
}

Note that for a binless (header-only or module interface-only) library you still need to list the system library in *.libs in addition to *.export.libs. See How do I make a header-only C/C++ library? for details.

See also How do I link the pthread library?