I reverted the earlier broken patch. I am including an updated patch
which warns only for real conversion, not for integral conversions. I
also updated the test case to include an integral conversion (int to
char) which doesn't emit the warning with the -Wreal-conversion flag.
Bootstrapped and tested on x86_64. Okay for google/gcc-4_8?
Thanks,
Sharad
2013-06-26 <l...@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: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 200448)
+++ doc/invoke.texi (working copy)
@@ -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. This warning is also enabled by @option{-Wconversion}.
+
@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 200448)
+++ 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
EnabledBy(Wconversion)
+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 200448)
+++ 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 200448)
+++ c-family/c-common.c (working copy)
@@ -2665,12 +2665,22 @@ unsafe_conversion_p (tree type, tree expr, bool pr
static void
conversion_warning (tree type, tree expr)
{
+ int warn_option;
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;
+ /* When either type is a floating point type, warn with
+ -Wreal-conversion instead of -Wconversion (-Wreal-conversion is a
+ subset of -Wconversion that only warns for conversions of real
+ types to integral types). */
+ warn_option = (warn_real_conversion
+ && (FLOAT_TYPE_P (type) || FLOAT_TYPE_P (expr_type)))
+ ? OPT_Wreal_conversion
+ : OPT_Wconversion;
+
switch (TREE_CODE (expr))
{
case EQ_EXPR:
@@ -2689,14 +2699,14 @@ conversion_warning (tree type, tree expr)
can hold the values 0 and -1) doesn't lose information - but
it does change the value. */
if (TYPE_PRECISION (type) == 1 && !TYPE_UNSIGNED (type))
- warning_at (loc, OPT_Wconversion,
+ warning_at (loc, warn_option,
"conversion to %qT from boolean expression", type);
return;
case REAL_CST:
case INTEGER_CST:
if (unsafe_conversion_p (type, expr, true))
- warning_at (loc, OPT_Wconversion,
+ warning_at (loc, warn_option,
"conversion to %qT alters %qT constant value",
type, expr_type);
return;
@@ -2715,7 +2725,7 @@ conversion_warning (tree type, tree expr)
default: /* 'expr' is not a constant. */
if (unsafe_conversion_p (type, expr, true))
- warning_at (loc, OPT_Wconversion,
+ warning_at (loc, warn_option,
"conversion to %qT from %qT may alter its value",
type, expr_type);
}
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 +1,25 @@
+// { 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 = 3.14;
+ float f = 1.8f;
+ 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" }
+ c = p;
+ int q;
+ q = func3(); // { dg-warning "conversion to" }
+}
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 +1,24 @@
+// { 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 = 3.14;
+ float f = 1.8f;
+ 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" }
+ c = p;
+ int q;
+ q = func3(); // { dg-warning "conversion to" }
+}
