Hi, Consider the the following code: // Header foo.h: const double FooLength; const double FooMass; // Source file foo.c: #include "foo.h" const double FooLength = 4.2; const double FooMass = 10.5; // Source file bar.c: #include foo.h ... This is non-standard C, but it is correct if you rely on the '-fcommon' feature of GCC which merges tentative definitions across translation units. I find '-fcommon' to be a convenient and useful feature because it allows you to omit 'extern' specifiers on declarations of global constants. My question is: if I rely on '-fcommon' in this way in my own software, is it likely to cause any problems for me down the line? For example, are there any plans to deprecate '-fcommon' in GCC in the future? Regards, Rob Henderson Additional notes: () The '-fcommon' functionality is described in K&R in a footnote (2nd edition, Sect. A10.2, pg. 227) as an "alternate formulation, ... usual in UNIX systems and recognised as a common extension by the Standard". () The GNU LD manual, Sect. 2.1, describes reliance on '-fcommon' as a "somewhat sloppy practice".
