Best practice for linking against libatomic?

[Simon Richter]

Hi,

On 1/12/26 11:59 PM, Florian Weimer wrote:

> It would be interesting to know which functionality needs libatomic.
> What are the linker errors you encountered?

Missing symbols, the ones in the build logs I have are:

  - __atomic_exchange_1
  - __atomic_fetch_add_2
  - __atomic_compare_exchange_1

There are a few weird ones, like

/usr/bin/ld: /tmp/ccXOVIUZ.ltrans0.ltrans.o: undefined reference to 
symbol '__atomic_exchange_1@@LIBATOMIC_1.0'

so for LTO, there seems to be an error path that can find the version, 
but then does not resolve the symbol -- these are fairly seldom though.

With gcc 16 making this change automatic, I suspect a lot of failures 
will go away, I'm not sure if that is portable though, or if a configure 
script is supposed to find out if libatomic needs to be linked, which 
some seem to do with varying degrees of success.

I mean, would it make sense to build an autoconf macro like 
"AC_LIB_ATOMIC([bool, int, void *])" that would determine if making any 
of the listed types atomic requires linking against libatomic?

    Simon