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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.lang.c
Subject: No warning at implicit removal of const. Was: relearning C: why
 does an in-place change to a char* segfault?
Date: Thu, 1 Aug 2024 17:40:26 +0300
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On Thu, 01 Aug 2024 08:06:57 +0000
Mark Summerfield <mark@qtrac.eu> wrote:

> This program segfaults at the commented line:
> 
> #include <ctype.h>
> #include <stdio.h>
> 
> void uppercase_ascii(char *s) {
>     while (*s) {
>         *s = toupper(*s); // SEGFAULT
>         s++;
>     }
> }
> 
> int main() {
>     char* text = "this is a test";
>     printf("before [%s]\n", text);
>     uppercase_ascii(text);
>     printf("after  [%s]\n", text);
> }
> 

The answers to your question are already given above, so I'd talk about
something else. Sorry about it.

To my surprise, none of the 3 major compilers that I tried issued the
warning at this line:
  char* text = "this is a test";
If implicit conversion of 'const char*' to 'char*' does not warrant
compiler warning than I don't know what does.
Is there something in the Standard that explicitly forbids diagnostic
for this sort of conversion?

BTW, all 3 compilers issue reasonable warnings when I write it slightly
differently:
  const char* ctext = "this is a test";
  char* text = ctext;

I am starting to suspect that compilers (and the Standard?) consider
string literals as being of type 'char*' rather than 'const char*'.