Re: Will autoconf work with -Werror=implicit-int and -Werror=implicit-function-declaration ?

[Paul Eggert]

On 2023-12-12 01:32, Arsen Arsenović wrote:

> Paul Eggert <eggert@cs.ucla.edu> writes:
> > Although it'll be helpful for Autoconf to work by default with those two
> > options, it's not essential because it's bad advice for builders to *configure*
> > with all the options suggested in "Compiler Options Hardening Guide for C and
> > C++"[1]. The advice should merely be to *build* with those options.
>
> These options tell compilers to work as the C standard requires.  They
> will soon not be flags that need to be added explicitly.  See:
> https://inbox.sourceware.org/87ttp3tek1.fsf@oldenburg.str.redhat.com/

Thanks for the heads-up; I wasn't aware of that effort. However, the 
behavior it's proposing (defaulting to errors for -Wint-conversion, 
Wreturn-mismatch, -Wdeclaration-missing-parameter-type, 
-Wincompatible-pointer-types) shouldn't be much of a problem for 
Autoconf. These warnings are less intrusive and controversial than the 
warning options suggested in [1] and I don't think they'll be much of a 
problem for Autoconf or for Autoconf-using programs.


> > This is because the recommended options include controversial ones like
> > -Wconversion that can be harmful in C code. The only way to pacify -Wconversion
> > is to complicate the code by inserting casts that can lower code safety and
> > quality. Even Gnulib, which goes far beyond [1] in recommending warning
> > options, disables -Wconversion.
>
> I'm not sure I agree that handling real lossy conversions lowers code
> quality, but this flag is not a behavior required by the standard, so I
> suppose not assuming it is OK.

Yes, although -Wconversion can sometimes be useful unfortunately it too 
often forces you to put in casts that can mask serious problems later. 
The C standard doesn't require -Wconversion diagnostics and I expect it 
never will.

[1]: 
https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++