[Bug web/82448] New: GCC web guide contains wrong information about Werror

[alexander.samoylov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82448

            Bug ID: 82448
           Summary: GCC web guide contains wrong information about Werror
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: web
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alexander.samoylov at gmail dot com
  Target Milestone: ---

The documentation guide
https://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Warning-Options.html is wrong. The
chapter "3.8 Options to Request or Suppress Warnings" tells that the option
-Werror= makes the specified warning into an error, but it is not so. Look at
the simple test:

~> gcc --version
gcc (Debian 4.3.2-1.1) 4.3.2
~> gcc -Wsequence-point -c -o test.o test.c
test.c: In function 'main':
test.c:24: warning: operation on 'Y1_Ptr' may be undefined
~> gcc -Werror=sequence-point -c -o test.o test.c
test.c: In function 'main':
test.c:24: warning: operation on 'Y1_Ptr' may be undefined

It means that -Werror= still does not turn any warning to an error, but the
guide for 4.3.2 tells that is does.
-Werror=<warning> started to work at some later GCC version. I don't know
which, but at least on GCC 4.8.4 it works for me:
$ gcc --version
gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
$ gcc -Werror=sequence-point -c -o test.o test.c
test1.c: In function ‘main’:
test1.c:24:16: error: operation on ‘Y1_Ptr’ may be undefined
[-Werror=sequence-point]
         *Y1_Ptr++ = *(Y1_Ptr - 1);
                ^
cc1: some warnings being treated as errors


Please, update each guide
https://gcc.gnu.org/onlinedocs/gcc-?.?.?/gcc/Warning-Options.html so that the
information about -Werror= is added only for the versions where it works. If
there are versions where is works partially (not for all warnings), please
refer to exact list of warnings with which it really works.

P.S.:
I wanted to use the references
https://gcc.gnu.org/onlinedocs/gcc-?.?.?/gcc/Warning-Options.html to compare
information about warnings between different versions and to find out from
which version -Werror=<warning> started to work. With the current wrong content
the guide is unusable for that.
I can install different GCC versions on the host to determine from which one
the option started to work, but it is a lot of work to do this way.

--
Best Regards,
Alexander.