[google/gcc-4_8] Port -Wreal-conversion warning

Hi,

This patch forward ports the -Wreal-conversion warning to
google/gcc-4_8 branch (google ref 39133-p2). I tweaked the patch a
little bit to avoid printing duplicate warnings when both -Wconversion
and -Wreal-conversion are specified. Also, I trimmed the test case to
avoid testing for integer-to-integer narrowing conversions as this
warning is about real conversions.

Bootstrapped and tested on x86_64. Okay for google/gcc-4_8?

Thanks,
Sharad

2013-06-24    <lcwu@google.com>

* doc/invoke.texi: Document new option -Wreal-conversion.
* c-family/c.opt: Handle new option.
* c-family/c-opts.c (c_common_post_options): Ditto.
* c-family/c-common.c (conversion_warning): Ditto.

testsuite/ChangeLog:

* testsuite/gcc.dg/Wreal-conversion-1.c: New test.
* testsuite/g++.dg/warn/Wreal-conversion-1.C: Ditto.

To avoid printing twice, can you just do

opt_type = (warn_conversion ? OPT_Wconversion : OPT_Wreal_conversion);
warning_at (loc, opt_type, ...);

David

On Mon, Jun 24, 2013 at 6:08 PM, Sharad Singhai <singhai@google.com> wrote:
> Hi,
>
> This patch forward ports the -Wreal-conversion warning to
> google/gcc-4_8 branch (google ref 39133-p2). I tweaked the patch a
> little bit to avoid printing duplicate warnings when both -Wconversion
> and -Wreal-conversion are specified. Also, I trimmed the test case to
> avoid testing for integer-to-integer narrowing conversions as this
> warning is about real conversions.
>
> Bootstrapped and tested on x86_64. Okay for google/gcc-4_8?
>
> Thanks,
> Sharad
>
> 2013-06-24    <lcwu@google.com>
>
> * doc/invoke.texi: Document new option -Wreal-conversion.
> * c-family/c.opt: Handle new option.
> * c-family/c-opts.c (c_common_post_options): Ditto.
> * c-family/c-common.c (conversion_warning): Ditto.
>
> testsuite/ChangeLog:
>
> * testsuite/gcc.dg/Wreal-conversion-1.c: New test.
> * testsuite/g++.dg/warn/Wreal-conversion-1.C: Ditto.
>
> Index: testsuite/gcc.dg/Wreal-conversion-1.c
> ===================================================================
> --- testsuite/gcc.dg/Wreal-conversion-1.c (revision 0)
> +++ testsuite/gcc.dg/Wreal-conversion-1.c (revision 0)
> @@ -0,0 +1,23 @@
> +// { dg-do compile }
> +// { dg-options "-Wreal-conversion" }
> +
> +#include <stddef.h>
> +
> +int func1(int a) {
> +  double f = a;
> +  return f;           // { dg-warning "conversion to" }
> +}
> +
> +double func3();
> +
> +void func2() {
> +  double g = 3.2;
> +  float f;
> +  int t = g;          // { dg-warning "conversion to" }
> +  int p;
> +  p = f;              // { dg-warning "conversion to" }
> +  func1(g);           // { dg-warning "conversion to" }
> +  char c = f;         // { dg-warning "conversion to" }
> +  int q;
> +  q = func3();        // { dg-warning "conversion to" }
> +}
> Index: testsuite/g++.dg/warn/Wreal-conversion-1.C
> ===================================================================
> --- testsuite/g++.dg/warn/Wreal-conversion-1.C (revision 0)
> +++ testsuite/g++.dg/warn/Wreal-conversion-1.C (revision 0)
> @@ -0,0 +1,24 @@
> +// { dg-do compile }
> +// { dg-options "-Wreal-conversion" }
> +
> +#include <stddef.h>
> +
> +int func1(int a) {
> +  double f = a;
> +  return f;           // { dg-warning "conversion to" }
> +}
> +
> +double func3();
> +
> +void func2() {
> +  double g = 3.2;
> +  float f;
> +  int t = g;          // { dg-warning "conversion to" }
> +  bool b = g;
> +  int p;
> +  p = f;              // { dg-warning "conversion to" }
> +  func1(g);           // { dg-warning "conversion to" }
> +  char c = f;         // { dg-warning "conversion to" }
> +  int q;
> +  q = func3();        // { dg-warning "conversion to" }
> +}
> Index: doc/invoke.texi
> ===================================================================
> --- doc/invoke.texi (revision 200359)
> +++ doc/invoke.texi (working copy)
> @@ -193,7 +193,7 @@ in the following sections.
>  -fno-default-inline  -fvisibility-inlines-hidden @gol
>  -fvisibility-ms-compat @gol
>  -fext-numeric-literals @gol
> --Wabi  -Wconversion-null  -Wctor-dtor-privacy @gol
> +-Wabi  -Wconversion-null -Wctor-dtor-privacy @gol
>  -Wdelete-non-virtual-dtor -Wliteral-suffix -Wnarrowing @gol
>  -Wnoexcept -Wnon-virtual-dtor  -Wreorder @gol
>  -Weffc++  -Wstrict-null-sentinel @gol
> @@ -237,7 +237,7 @@ Objective-C and Objective-C++ Dialects}.
>  -Wno-attributes -Wno-builtin-macro-redefined @gol
>  -Wc++-compat -Wc++11-compat -Wcast-align  -Wcast-qual  @gol
>  -Wchar-subscripts -Wclobbered  -Wcomment @gol
> --Wconversion  -Wcoverage-mismatch  -Wno-cpp  -Wno-deprecated  @gol
> +-Wconversion -Wreal-conversion -Wcoverage-mismatch  -Wno-cpp
> -Wno-deprecated  @gol
>  -Wno-deprecated-declarations -Wdisabled-optimization  @gol
>  -Wno-div-by-zero -Wdouble-promotion -Wempty-body  -Wenum-compare @gol
>  -Wno-endif-labels -Werror  -Werror=* @gol
> @@ -4452,6 +4452,12 @@ reference to them. Warnings about conversions betw
>  unsigned integers are disabled by default in C++ unless
>  @option{-Wsign-conversion} is explicitly enabled.
>
> +@item -Wreal-conversion
> +@opindex Wreal-conversion
> +@opindex Wno-real-conversion
> +Warn for implicit type conversions from real (@code{double} or @code{float})
> +to integral values.
> +
>  @item -Wno-conversion-null @r{(C++ and Objective-C++ only)}
>  @opindex Wconversion-null
>  @opindex Wno-conversion-null
> Index: c-family/c.opt
> ===================================================================
> --- c-family/c.opt (revision 200359)
> +++ c-family/c.opt (working copy)
> @@ -677,6 +677,10 @@ Wsign-compare
>  C ObjC C++ ObjC++ EnabledBy(Wextra)
>  ;
>
> +Wreal-conversion
> +C ObjC C++ ObjC++ Var(warn_real_conversion) Init(-1) Warning
> +Warn for implicit type conversions from real to integral values
> +
>  Wsign-conversion
>  C ObjC C++ ObjC++ Var(warn_sign_conversion) LangEnabledBy(C ObjC,Wconversion)
>  Warn for implicit type conversions between signed and unsigned integers
> Index: c-family/c-opts.c
> ===================================================================
> --- c-family/c-opts.c (revision 200359)
> +++ c-family/c-opts.c (working copy)
> @@ -876,6 +876,12 @@ c_common_post_options (const char **pfilename)
>    if (warn_packed_bitfield_compat == -1)
>      warn_packed_bitfield_compat = 1;
>
> +  /* Enable warning for converting real values to integral values
> +     when -Wconversion is specified (unless disabled through
> +     -Wno-real-conversion).  */
> +  if (warn_real_conversion == -1)
> +    warn_real_conversion = warn_conversion;
> +
>    /* Special format checking options don't work without -Wformat; warn if
>       they are used.  */
>    if (!warn_format)
> Index: c-family/c-common.c
> ===================================================================
> --- c-family/c-common.c (revision 200359)
> +++ c-family/c-common.c (working copy)
> @@ -2668,7 +2668,7 @@ conversion_warning (tree type, tree expr)
>    tree expr_type = TREE_TYPE (expr);
>    location_t loc = EXPR_LOC_OR_HERE (expr);
>
> -  if (!warn_conversion && !warn_sign_conversion)
> +  if (!warn_conversion && !warn_sign_conversion && !warn_real_conversion)
>      return;
>
>    switch (TREE_CODE (expr))
> @@ -2715,9 +2715,17 @@ conversion_warning (tree type, tree expr)
>
>      default: /* 'expr' is not a constant.  */
>        if (unsafe_conversion_p (type, expr, true))
> - warning_at (loc, OPT_Wconversion,
> -    "conversion to %qT from %qT may alter its value",
> -    type, expr_type);
> +      {
> +        /* Do not print the same warning twice. */
> +        bool printed =
> +            warning_at (loc, OPT_Wreal_conversion,
> +                        "conversion to %qT from %qT may alter its value",
> +                        type, expr_type);
> +        if (!printed)
> +          warning_at (loc, OPT_Wconversion,
> +                      "conversion to %qT from %qT may alter its value",
> +                      type, expr_type);
> +      }
>      }
>  }