Is section order preserved in C?

Andrew Haley aph@redhat.com
Wed Jun 16 13:11:00 GMT 2010


On 06/16/2010 03:03 AM, David VomLehn wrote:
> This is probably an obscure question, but is the order that C puts things
> in sections with the __attribute((section("secA"))) always the same as
> the order in which they appear in the source file. For example:
> 
> 	void f(void)
> 	{
> 		static int a1 __attribute__((section("A")));
> 		static int b1 __attribute__((section("B")));
> 	}
> 	void g(void)
> 	{
> 		static int a2 __attribute__((section("A")));
> 		static int b2 __attribute__((section("B")));
> 	}
> 
> So, can I count on the storage for a1 being followed by storage for a2 in
> section A and the storage for b1 being followed by storage for b2?
> 
> It makes my life a bit easier if this is true, but I'm rather sure the C
> standard doesn't guarantee it, and wouldn't be surprised if it weren't
> true. I only care about ordering within sections, not the order in which
> sections appear.

No.  Section ordering is controlled by the linker.  If you need some
specific order you can write a link script to do it, but all this is
way outside the subject of gcc.

Andrew.



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