[Bug c/82919] New: Docs don't mention -Wimplicit-int is enabled in C99 mode

[antox at ml dot lv]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82919

            Bug ID: 82919
           Summary: Docs don't mention -Wimplicit-int is enabled in C99
                    mode
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antox at ml dot lv
  Target Milestone: ---

-Wimplicit-int is enabled by default in C99 mode (or later) just like
-Wimplicit-function-declaration. This is not documented (e.g.
https://gcc.gnu.org/onlinedocs/gcc-7.2.0/gcc/Warning-Options.html):

----
-Wimplicit-int (C and Objective-C only)

    Warn when a declaration does not specify a type. This warning is enabled by
-Wall.

-Wimplicit-function-declaration (C and Objective-C only)

    Give a warning whenever a function is used before being declared. In C99
mode (-std=c99 or -std=gnu99), this warning is enabled by default and it is
made into an error by -pedantic-errors. This warning is also enabled by -Wall.

-Wimplicit (C and Objective-C only)
    Same as -Wimplicit-int and -Wimplicit-function-declaration.  This warning
is enabled by -Wall.
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