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Re: hzoli change: $foo:s//r/

>Yes, it is really a good idea.  But if it is really guaranteed that externs
>are initialized to zere therese initializations are unnecessary.  The fact
>that zsh worked so far shows that it is quite safe to assume that global
>variables are initialized to zero, but what is in the ANSI-C standard?

ANSI requires that all objects of static storage duration (i.e.
non-auto variables) are initialised to zero(*), except when explicitly
initialised to something else.  (*) Integers are initialised to
all-bits zero, which is numerically zero, but floating-point values are
initialised to floating-point zero, and pointers are initialised to a
NULL value which is not required to be all-bits zero.

This requirement has existed throughout C's lifetime; it initially
appeared, I think, because such variables under Unix are put in the BSS
area, which the kernel initialises to all-bits zero.  The ANSI
committee had no choice but to uphold the assumption made by most C
programmers that this initialisation would take place, but they made
the required initialisation effectively "numerically zero" rather than
"all-bits zero" because of the unspecified nature of pointer and
floating-point representations.

Under Unix it's quite safe to assume that this initialisation will
happen (to all-bits zero, which under Unix is good for a NULL pointer)
even in languages that make no such guarantee.


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