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NNTP-Posting-Date: Thu, 08 Jun 2017 10:56:17 -0500
From: Gareth Owen <gwowen@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: sizeof environment variables array = 1?
References: <ohbpd7$5r3$2@dont-email.me>
Date: Thu, 08 Jun 2017 16:56:17 +0100
Message-ID: <878tl2v5ge.fsf@gmail.com>
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Xref: csiph.com comp.lang.c:111826

DFS <nospam@dfs.com> writes:

> int main(int argc, char *argv[], char *env[])
> {
>   printf("%d\n",sizeof(env)/sizeof(env[0]));
>   return(0);
> )
>
> Output is 1.
>
> Why?

Anything that looks like an array object - when used in the argument
list of a function, is not an array object, but "decays" into a pointer.

so in

int foo(char *arr1[12])
{
   char *arr2[12];
   char **arr3;
}

arr1 and arr3 have the same type, even though
arr1 and arr2 have the same declaration.

A misfeature, but an explicable one.

There is no way to obtain the size of arr1 in foo() without passing it
in explicitly (or counting them using a sentinel such as NULL to mark
the end, as is done with environment variables)