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From: James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups: comp.lang.c++
Subject: Re: Pre-main construction order in modules
Date: Sun, 30 Mar 2025 10:38:57 -0400
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On 3/30/25 4:57 AM, Muttley@DastardlyHQ.org wrote:
> I was curious about the order in which objects get constructed in modules
> before main gets called. It seems with both Clang and gcc its the order in
> which the modules were linked together to form the runnable binary so if
> the link order was m1.o m2.o then anything in m1 would get constructed first.
> Vice verca if you switch the order.
> 
> Is this codified in the standard or is it left up to compiler and linker
> writers to decide how they order this?

Section 6.9.3.3 does in fact impose many constraints on the sequence in
which non-local objects with static storage duration get initialized.
However, all of the sequence requirements are only between objects
defined in the same translation unit. Also, it's implementation-defined
which of those initializations occur before the start of main().