/ curl Public
Check whether atomics can link rather than just compile. #9190
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Some build toolchains support C11 atomics (i.e.,
_Atomictypes), but will not link the associated atomics runtime unless a flag is passed. In such an environment, linking an application with
libcurl.acan fail due to undefined symbols for atomic load/store functions.
I encountered this behavior when upgrading
curlto 7.84.0 and attempting to build with Solaris Studio 12.6. Solaris provides the flag
-xatomic=[gcc | studio], allowing users to link to one of two atomics runtime implementations. However, if the user does not provide this flag, then neither runtime is linked. This led to builds failing in CI, because:
HAVE_ATOMICSmacro was given a definition.
My suggested fix is to:
_Atomicsupport to assign to the variable after initializing it. For toolchains that implement atomic loads/stores by linking external libraries, this ensures that such a function will be required.