Did some additional research. The code can work asis when _ALL_SOURCE is undefined. Or, in other words - there does not have to be a variable syntax issue or separate code for AIX.As you read this - please remember that since issue#32143 was 'resolved' AIX cannot compile.*https://www.gnu.org/software/autoconf/manual/autoconf-2.64/html_node/Posix-Variants.htmldescribes _ALL_SOURCE as a macro for AIX3.Looking at AIX: /usr/include/sys/types.h - by undefining _ALL_SOURCE the typedefs in the header files are equivalent enough that the new code added for os.statvfs(path) is compiled by both gcc and xlc.As examples (from Centos)/usr/include/bits/typesizes.h:72:#define __FSID_T_TYPE          struct { int __val[2]; }And from AIX: * /usr/include/sys/types.h  +360  / * typedef for the File System Identifier (fsid).  This must correspond  +361    * to the "struct fsid" structure in _ALL_SOURCE below.  +362    * /  +363  typedef struct fsid_t {  +364  #ifdef __64BIT_KERNEL  +365          unsigned long val[2];  +366  #else  / * __64BIT_KERNEL * /  +367  #ifdef _ALL_SOURCE  +368          unsigned int val[2];  +369  #else  / * _ALL_SOURCE * /  +370          unsigned int __val[2];  +371  #endif / * _ALL_SOURCE * /  +372  #endif / * __64BIT_KERNEL * /  +373  } fsid_t; */(Note - a variation of the text above was in the pull requesthttps://github.com/python/cpython/pull/4972. Per reviewer request - this is removed and a discussion is now open here.)Thank you for your comments.