Re: [PATCH] Add -Wmissing-variable-declarations [PR65213].

[Hamza Mahfooz <someguy@effective-light.com>]

Ping?

On Tue, Jun 13 2023 at 09:05:29 AM -04:00:00, Hamza Mahfooz 
<someguy@effective-light.com> wrote:
> Resolves:
> PR c/65213 - Extend -Wmissing-declarations to variables [i.e. add
> -Wmissing-variable-declarations]
> 
> gcc/c-family/ChangeLog:
> 
> 	PR c/65213
> 	* c.opt (-Wmissing-variable-declarations): New option.
> 
> gcc/c/ChangeLog:
> 
> 	PR c/65213
> 	* c-decl.cc (start_decl): Handle -Wmissing-variable-declarations
> 
> gcc/ChangeLog:
> 
> 	PR c/65213
> 	* doc/invoke.texi (-Wmissing-variable-declarations): Document
> 	new option.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c/65213
> 	* gcc.dg/Wmissing-variable-declarations.c: New test.
> 
> Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
> ---
>  gcc/c-family/c.opt                            |  4 +++
>  gcc/c/c-decl.cc                               | 10 +++++-
>  gcc/doc/invoke.texi                           | 11 +++++--
>  .../gcc.dg/Wmissing-variable-declarations.c   | 33 
> +++++++++++++++++++
>  4 files changed, 55 insertions(+), 3 deletions(-)
>  create mode 100644 
> gcc/testsuite/gcc.dg/Wmissing-variable-declarations.c
> 
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index cead1995561..42ad447f39b 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -1043,6 +1043,10 @@ Wmissing-prototypes
>  C ObjC Var(warn_missing_prototypes) Warning
>  Warn about global functions without prototypes.
> 
> +Wmissing-variable-declarations
> +C ObjC Var(warn_missing_variable_declarations) Warning
> +Warn about global variables without previous declarations.
> +
>  Wmudflap
>  C ObjC C++ ObjC++ WarnRemoved
> 
> diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
> index 1af51c4acfc..8e276b2a846 100644
> --- a/gcc/c/c-decl.cc
> +++ b/gcc/c/c-decl.cc
> @@ -5340,6 +5340,7 @@ start_decl (struct c_declarator *declarator, 
> struct c_declspecs *declspecs,
>  	    location_t *lastloc /* = NULL */)
>  {
>    tree decl;
> +  tree old_decl;
>    tree tem;
>    tree expr = NULL_TREE;
>    enum deprecated_states deprecated_state = DEPRECATED_NORMAL;
> @@ -5360,7 +5361,9 @@ start_decl (struct c_declarator *declarator, 
> struct c_declspecs *declspecs,
>    if (!decl || decl == error_mark_node)
>      return NULL_TREE;
> 
> -  if (tree lastdecl = lastloc ? lookup_last_decl (decl) : NULL_TREE)
> +  old_decl = lookup_last_decl (decl);
> +
> +  if (tree lastdecl = lastloc ? old_decl : NULL_TREE)
>      if (lastdecl != error_mark_node)
>        *lastloc = DECL_SOURCE_LOCATION (lastdecl);
> 
> @@ -5372,6 +5375,11 @@ start_decl (struct c_declarator *declarator, 
> struct c_declspecs *declspecs,
>        && TREE_PUBLIC (decl))
>      warning (OPT_Wmain, "%q+D is usually a function", decl);
> 
> +  if (warn_missing_variable_declarations && VAR_P (decl)
> +      && !DECL_EXTERNAL (decl) && TREE_PUBLIC (decl) && old_decl == 
> NULL_TREE)
> +    warning_at (DECL_SOURCE_LOCATION (decl), 
> OPT_Wmissing_variable_declarations,
> +		"no previous declaration for %qD", decl);
> +
>    if (initialized)
>      /* Is it valid for this decl to have an initializer at all?
>         If not, set INITIALIZED to zero, which will indirectly
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 8fa3f9fae01..e9b51842234 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -496,8 +496,8 @@ Objective-C and Objective-C++ Dialects}.
> 
>  @item C and Objective-C-only Warning Options
>  @gccoptlist{-Wbad-function-cast  -Wmissing-declarations
> --Wmissing-parameter-type  -Wmissing-prototypes  -Wnested-externs
> --Wold-style-declaration  -Wold-style-definition
> +-Wmissing-parameter-type -Wmissing-prototypes 
> -Wmissing-variable-declarations
> +-Wnested-externs -Wold-style-declaration  -Wold-style-definition
>  -Wstrict-prototypes  -Wtraditional  -Wtraditional-conversion
>  -Wdeclaration-after-statement  -Wpointer-sign}
> 
> @@ -9565,6 +9565,13 @@ provide prototypes and a non-matching 
> declaration declares an
>  overload rather than conflict with an earlier declaration.
>  Use @option{-Wmissing-declarations} to detect missing declarations 
> in C++.
> 
> +@opindex Wmissing-variable-declarations
> +@opindex Wno-missing-variable-declarations
> +@item -Wmissing-variable-declarations @r{(C and Objective-C only)}
> +Warn if a global variable is defined without a previous declaration.
> +Use this option to detect global variables that do not have a 
> matching
> +extern declaration in a header file.
> +
>  @opindex Wmissing-declarations
>  @opindex Wno-missing-declarations
>  @item -Wmissing-declarations
> diff --git a/gcc/testsuite/gcc.dg/Wmissing-variable-declarations.c 
> b/gcc/testsuite/gcc.dg/Wmissing-variable-declarations.c
> new file mode 100644
> index 00000000000..b292dbe8c22
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/Wmissing-variable-declarations.c
> @@ -0,0 +1,33 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Wmissing-variable-declarations" } */
> +
> +int b0; /* { dg-warning "no previous declaration for 'b0'" } */
> +
> +int b1 = 1; /* { dg-warning "no previous declaration for 'b1'" } */
> +
> +int b2; /* { dg-warning "no previous declaration for 'b2'" } */
> +int b2 = 2;
> +
> +struct {
> +    int g0;
> +} b3; /* { dg-warning "no previous declaration for 'b3'" } */
> +
> +int b4; /* { dg-warning "no previous declaration for 'b4'" } */
> +int b4 = 3;
> +extern int b4;
> +
> +static int g1;
> +
> +void g2(void);
> +
> +extern int g3;
> +int g3;
> +int g3 = 4;
> +
> +struct g4 {
> +    int g5;
> +};
> +
> +void g6(void) {
> +    int g7;
> +}
> --
> 2.40.1
>