clang recently added a new warning -Wexpansion-to-defined, which
warns when `defined' is used outside a #if expression (including the
case of a macro that is then used in a #if expression).
While I disagree with their inclusion of the warning to -Wall, I think
it is a good addition overall. First, it is a logical extension of the
existing warning for breaking defined across a macro and its caller.
Second, it is good to make these warnings for `defined' available with
a command-line option other than -pedantic. In fact this warning is
not mandated by the standard and thus is a strange case of a non-pedwarn
enabled by -pedantic. As a side effect of using the command-line parsing
machinery to attach the new warning to -pedantic, it would become an
error for -pedantic-errors, which would be weird for a diagnostic that
is not mandated by the standard.
This patch adds -Wexpansion-to-defined, and enables it automatically
for -Wextra instead of -pedantic.
Bootstrapped and regression tested x86_64-pc-linux-gnu, ok?
Paolo
libcpp:
2016-08-09 Paolo Bonzini <bonz...@gnu.org>
* include/cpplib.h (struct cpp_options): Add new member
warn_expansion_to_defined.
(CPP_W_EXPANSION_TO_DEFINED): New enum member.
* expr.c (parse_defined): Warn for all uses of "defined"
in macros, and tie warning to CPP_W_EXPANSION_TO_DEFINED.
* system.h (HAVE_DESIGNATED_INITIALIZERS): Do not use
"defined" in macros.
gcc:
2016-08-09 Paolo Bonzini <bonz...@gnu.org>
* system.h (HAVE_DESIGNATED_INITIALIZERS,
HAVE_DESIGNATED_UNION_INITIALIZERS): Do not use
"defined" in macros.
gcc/c-family:
2016-08-09 Paolo Bonzini <bonz...@gnu.org>
* c.opt (Wexpansion-to-defined): New.
gcc/doc:
2016-08-09 Paolo Bonzini <bonz...@gnu.org>
* cpp.texi (Defined): Mention -Wexpansion-to-defined.
* cppopts.texi (Invocation): Document -Wexpansion-to-defined.
* invoke.texi (Warning Options): Document -Wexpansion-to-defined.
gcc/testsuite:
2016-08-09 Paolo Bonzini <bonz...@gnu.org>
* gcc.dg/cpp/defined.c: Mark newly introduced warnings. Adjust
options to include -Wexpansion-to-defined.
* gcc.dg/cpp/defined-no-Wexpansion-to-defined.c,
gcc.dg/cpp/defined-Wextra-Wno-expansion-to-defined.c,
gcc.dg/cpp/defined-Wextra.c: New testcases.
Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt (revision 239276)
+++ gcc/c-family/c.opt (working copy)
@@ -506,6 +506,10 @@
C ObjC C++ ObjC++ Var(warn_double_promotion) Warning
Warn about implicit conversions from \"float\" to \"double\".
+Wexpansion-to-defined
+C ObjC C++ ObjC++ CPP(warn_expansion_to_defined)
CppReason(CPP_W_EXPANSION_TO_DEFINED) Var(cpp_warn_expansion_to_defined)
Init(0) Warning EnabledBy(Wextra)
+Warn if \"defined\" is used outside #if.
+
Wimplicit-function-declaration
C ObjC Var(warn_implicit_function_declaration) Init(-1) Warning
LangEnabledBy(C ObjC,Wimplicit)
Warn about implicit function declarations.
Index: gcc/doc/cpp.texi
===================================================================
--- gcc/doc/cpp.texi (revision 239276)
+++ gcc/doc/cpp.texi (working copy)
@@ -3342,7 +3342,8 @@
the C standard says the behavior is undefined. GNU cpp treats it as a
genuine @code{defined} operator and evaluates it normally. It will warn
wherever your code uses this feature if you use the command-line option
-@option{-pedantic}, since other compilers may handle it differently.
+@option{-Wextra}, since other compilers may handle it differently. The
+warning can also be enabled individually with @option{-Wexpansion-to-defined}.
@node Else
@subsection Else
Index: gcc/doc/cppopts.texi
===================================================================
--- gcc/doc/cppopts.texi (revision 239276)
+++ gcc/doc/cppopts.texi (working copy)
@@ -120,6 +120,12 @@
@samp{#if} directive, outside of @samp{defined}. Such identifiers are
replaced with zero.
+@item -Wexpansion-to-defined
+@opindex Wexpansion-to-defined
+Warn whenever @samp{defined} is encountered in the expansion of a macro
+(including the case where the macro is expanded by an @samp{#if} directive).
+Such usage is not portable.
+
@item -Wunused-macros
@opindex Wunused-macros
Warn about macros defined in the main file that are unused. A macro
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 239276)
+++ gcc/doc/invoke.texi (working copy)
@@ -4914,6 +4914,12 @@
construct, known from C++, was introduced with ISO C99 and is by default
allowed in GCC@. It is not supported by ISO C90. @xref{Mixed Declarations}.
+@item -Wexpansion-to-defined
+@opindex Wexpansion-to-defined
+Warn whenever @samp{defined} is encountered in the expansion of a macro.
+(including the case where the macro is expanded by an @samp{#if} directive).
+This warning is also enabled by @option{-Wextra}.
+
@item -Wundef
@opindex Wundef
@opindex Wno-undef
Index: gcc/system.h
===================================================================
--- gcc/system.h (revision 239276)
+++ gcc/system.h (working copy)
@@ -577,16 +577,22 @@
/* 1 if we have C99 designated initializers. */
#if !defined(HAVE_DESIGNATED_INITIALIZERS)
+#ifdef __cplusplus
+#define HAVE_DESIGNATED_INITIALIZERS 0
+#else
#define HAVE_DESIGNATED_INITIALIZERS \
- (((GCC_VERSION >= 2007) || (__STDC_VERSION__ >= 199901L)) \
- && !defined(__cplusplus))
+ (((GCC_VERSION >= 2007) || (__STDC_VERSION__ >= 199901L))
#endif
+#endif
#if !defined(HAVE_DESIGNATED_UNION_INITIALIZERS)
+#ifdef __cplusplus
+#define HAVE_DESIGNATED_UNION_INITIALIZERS (GCC_VERSION >= 4007)
+#else
#define HAVE_DESIGNATED_UNION_INITIALIZERS \
- (((GCC_VERSION >= 2007) || (__STDC_VERSION__ >= 199901L)) \
- && (!defined(__cplusplus) || (GCC_VERSION >= 4007)))
+ (((GCC_VERSION >= 2007) || (__STDC_VERSION__ >= 199901L))
#endif
+#endif
#if HAVE_SYS_STAT_H
# include <sys/stat.h>
Index: gcc/testsuite/gcc.dg/cpp/defined-Wextra-Wno-expansion-to-defined.c
===================================================================
--- gcc/testsuite/gcc.dg/cpp/defined-Wextra-Wno-expansion-to-defined.c
(revision 0)
+++ gcc/testsuite/gcc.dg/cpp/defined-Wextra-Wno-expansion-to-defined.c
(working copy)
@@ -0,0 +1,30 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc. */
+
+/* { dg-do preprocess } */
+/* { dg-options "-Wextra -Wno-expansion-to-defined" } */
+
+/* Use of defined in different contexts. */
+
+/* Source: Neil Booth, 29 Oct 2000, Zack Weinberg 11 Dec 2000. */
+
+#define Z
+
+#define bad0 defined Z
+#if !bad0 /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
+#define bad1 defined
+#if !bad1 Z /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
+#if !bad1 (Z) /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
+#define bad2 defined (Z
+#if !bad2) /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
Index: gcc/testsuite/gcc.dg/cpp/defined-Wextra.c
===================================================================
--- gcc/testsuite/gcc.dg/cpp/defined-Wextra.c (revision 0)
+++ gcc/testsuite/gcc.dg/cpp/defined-Wextra.c (working copy)
@@ -0,0 +1,30 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc. */
+
+/* { dg-do preprocess } */
+/* { dg-options "-Wextra" } */
+
+/* Use of defined in different contexts. */
+
+/* Source: Neil Booth, 29 Oct 2000, Zack Weinberg 11 Dec 2000. */
+
+#define Z
+
+#define bad0 defined Z
+#if !bad0 /* { dg-warning "may not be portable" } */
+#error Z is defined
+#endif
+
+#define bad1 defined
+#if !bad1 Z /* { dg-warning "may not be portable" } */
+#error Z is defined
+#endif
+
+#if !bad1 (Z) /* { dg-warning "may not be portable" } */
+#error Z is defined
+#endif
+
+#define bad2 defined (Z
+#if !bad2) /* { dg-warning "may not be portable" } */
+#error Z is defined
+#endif
+
Index: gcc/testsuite/gcc.dg/cpp/defined-no-Wexpansion-to-defined.c
===================================================================
--- gcc/testsuite/gcc.dg/cpp/defined-no-Wexpansion-to-defined.c (revision 0)
+++ gcc/testsuite/gcc.dg/cpp/defined-no-Wexpansion-to-defined.c (working copy)
@@ -0,0 +1,30 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc. */
+
+/* { dg-do preprocess } */
+/* { dg-options "-ansi -pedantic-errors" } */
+
+/* Use of defined in different contexts. */
+
+/* Source: Neil Booth, 29 Oct 2000, Zack Weinberg 11 Dec 2000. */
+
+#define Z
+
+#define bad0 defined Z
+#if !bad0 /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
+#define bad1 defined
+#if !bad1 Z /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
+#if !bad1 (Z) /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
+#define bad2 defined (Z
+#if !bad2) /* { dg-bogus "may not be portable" } */
+#error Z is defined
+#endif
+
Index: gcc/testsuite/gcc.dg/cpp/defined.c
===================================================================
--- gcc/testsuite/gcc.dg/cpp/defined.c (revision 239276)
+++ gcc/testsuite/gcc.dg/cpp/defined.c (working copy)
@@ -1,6 +1,7 @@
/* Copyright (C) 2000 Free Software Foundation, Inc. */
/* { dg-do preprocess } */
+/* { dg-options "-ansi -pedantic-errors -Wexpansion-to-defined" } */
/* Tests behavior of the defined operator. */
@@ -21,7 +22,7 @@
/* The behavior of "defined" when it comes from a macro expansion is
now documented. */
-#if is_Z_defined
+#if is_Z_defined /* { dg-warning "may not be portable" } */
#error Macro expanding into defined operator test 1
#endif
@@ -31,7 +32,7 @@
#error Z is defined
#endif
-#if !is_Z_defined
+#if !is_Z_defined /* { dg-warning "may not be portable" } */
#error Macro expanding into defined operator test 2
#endif
@@ -53,7 +54,7 @@
/* The behavior of "defined" when it comes from a macro expansion is
now documented. */
-#if is_Z_defined
+#if is_Z_defined /* { dg-warning "may not be portable" } */
#error Macro expanding into defined operator test 1
#endif
@@ -63,7 +64,7 @@
#error Z is defined
#endif
-#if !is_Z_defined
+#if !is_Z_defined /* { dg-warning "may not be portable" } */
#error Macro expanding into defined operator test 2
#endif
Index: libcpp/expr.c
===================================================================
--- libcpp/expr.c (revision 239276)
+++ libcpp/expr.c (working copy)
@@ -947,9 +947,11 @@
if (node)
{
- if (pfile->context != initial_context && CPP_PEDANTIC (pfile))
- cpp_error (pfile, CPP_DL_WARNING,
- "this use of \"defined\" may not be portable");
+ if ((pfile->context != initial_context
+ || initial_context != &pfile->base_context)
+ && CPP_OPTION (pfile, warn_expansion_to_defined))
+ cpp_warning (pfile, CPP_W_EXPANSION_TO_DEFINED,
+ "this use of \"defined\" may not be portable");
_cpp_mark_macro_used (node);
if (!(node->flags & NODE_USED))
Index: libcpp/include/cpplib.h
===================================================================
--- libcpp/include/cpplib.h (revision 239276)
+++ libcpp/include/cpplib.h (working copy)
@@ -410,6 +410,10 @@
/* Nonzero means warn if undefined identifiers are evaluated in an #if. */
unsigned char warn_undef;
+ /* Nonzero means warn if "defined" is encountered in a place other than
+ an #if. */
+ unsigned char warn_expansion_to_defined;
+
/* Nonzero means warn of unused macros from the main file. */
unsigned char warn_unused_macros;
@@ -1025,7 +1029,8 @@
CPP_W_DATE_TIME,
CPP_W_PEDANTIC,
CPP_W_C90_C99_COMPAT,
- CPP_W_CXX11_COMPAT
+ CPP_W_CXX11_COMPAT,
+ CPP_W_EXPANSION_TO_DEFINED
};
/* Output a diagnostic of some kind. */
Index: libcpp/system.h
===================================================================
--- libcpp/system.h (revision 239276)
+++ libcpp/system.h (working copy)
@@ -375,10 +375,13 @@
??? C99 designated initializers are not supported by most C++
compilers, including G++. -- gdr, 2005-05-18 */
#if !defined(HAVE_DESIGNATED_INITIALIZERS)
+#ifdef __cplusplus
+#define HAVE_DESIGNATED_INITIALIZERS 0
+#else
#define HAVE_DESIGNATED_INITIALIZERS \
- (!defined(__cplusplus) \
- && ((GCC_VERSION >= 2007) || (__STDC_VERSION__ >= 199901L)))
+ ((GCC_VERSION >= 2007) || (__STDC_VERSION__ >= 199901L))
#endif
+#endif
#ifndef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *) 0)->MEMBER)
