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Wed, 11 Nov 2020 17:11:09 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Felipe Contreras Date: Wed, 11 Nov 2020 19:10:58 -0600 Message-ID: Subject: Re: Bug with unset variables To: Mikael Magnusson Cc: Zsh hackers list Content-Type: text/plain; charset="UTF-8" X-Seq: 47543 Archived-At: X-Loop: zsh-workers@zsh.org Errors-To: zsh-workers-owner@zsh.org Precedence: list Precedence: bulk Sender: zsh-workers-request@zsh.org X-no-archive: yes List-Id: List-Help: List-Subscribe: List-Unsubscribe: List-Post: List-Owner: List-Archive: Archived-At: On Wed, Nov 11, 2020 at 6:20 PM Mikael Magnusson wrote: > On 11/11/20, Felipe Contreras wrote: > > That being said, the most similar to shell's "declare var" in C is > > "char *var" which defaults to null on most systems. > > This is certainly not true, just for the record. Variables in global > or static scope are initialized to 0 regardless of type, whereas > others are uninitialized (meaning they contain garbage, not that they > magically know that they haven't been assigned to). The C standard says accessing an uninitialized variable results in *undefined* behavior, it doesn't say the variable *must* contain garbage. The variable *may* contain garbage, but not necessarily so. However, "static char *var" is *always* initialized to null. Either way, what *never* happens is var pointing to an empty string. -- Felipe Contreras