Warn about this:
void f(int x; int x; int x);
This would allow eventually adding another semicolon in function
prototypes to separate a different feature.
So, make multiple lists of forward declarations of parameters
obsolescent, and produce a new diagnostic,
-Wmultiple-parameter-fwd-decl-lists, which diagnoses uses of this
obsolescent syntax.
Forward declarations of parameters are a rarely used feature, AFAIK,
(and having more than one would be even rarer) so this shouldn't be
problematic in -Wextra. Eventually, we may want to move this into
a default diagnostic, and later an error.
gcc/c-family/ChangeLog:
* c.opt: Add -Wmultiple-parameter-fwd-decl-lists
gcc/c/ChangeLog:
* c-decl.cc (c_scope): Rename {warned > had}_forward_parm_decls.
(mark_forward_parm_decls): Add
-Wmultiple-parameter-fwd-decl-lists.
gcc/ChangeLog:
* doc/invoke.texi: Document the new
-Wmultiple-parameter-fwd-decl-lists.
gcc/testsuite/ChangeLog:
* gcc.gd/Wmultiple-parameter-fwd-decl-lists.c: New test.
Cc: Christopher Bazley <chris.bazley.w...@gmail.com>
Cc: Martin Uecker <uec...@tugraz.at>
Signed-off-by: Alejandro Colomar <a...@kernel.org>
---
gcc/c-family/c.opt | 4 ++++
gcc/c/c-decl.cc | 16 +++++++++-------
gcc/doc/extend.texi | 2 +-
gcc/doc/invoke.texi | 13 ++++++++++++-
.../gcc.dg/Wmultiple-parameter-fwd-decl-lists.c | 6 ++++++
5 files changed, 32 insertions(+), 9 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/Wmultiple-parameter-fwd-decl-lists.c
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 3f5e2f0874d..4fd8770b65c 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1086,6 +1086,10 @@ Wmultiple-inheritance
C++ ObjC++ Var(warn_multiple_inheritance) Warning
Warn on direct multiple inheritance.
+Wmultiple-parameter-fwd-decl-lists
+C ObjC Var(warn_multiple_parameter_fwd_decl_lists) Warning EnabledBy(Wextra)
+Warn for multiple lists of forward declarations of function parameters.
+
Wmultistatement-macros
C ObjC C++ ObjC++ Var(warn_multistatement_macros) Warning LangEnabledBy(C ObjC
C++ ObjC++,Wall)
Warn about unsafe macros expanding to multiple statements used as a body of a
clause such as if, else, while, switch, or for.
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 62a0545947e..12c7994c412 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -507,7 +507,7 @@ struct GTY((chain_next ("%h.outer"))) c_scope {
/* True if we already complained about forward parameter decls
in this scope. This prevents double warnings on
foo (int a; int b; ...) */
- BOOL_BITFIELD warned_forward_parm_decls : 1;
+ BOOL_BITFIELD had_forward_parm_decls : 1;
/* True if this is the outermost block scope of a function body.
This scope contains the parameters, the local variables declared
@@ -6269,12 +6269,14 @@ mark_forward_parm_decls (void)
{
struct c_binding *b;
- if (pedantic && !current_scope->warned_forward_parm_decls)
- {
- pedwarn (input_location, OPT_Wpedantic,
- "ISO C forbids forward parameter declarations");
- current_scope->warned_forward_parm_decls = true;
- }
+ if (current_scope->had_forward_parm_decls)
+ warning_at (input_location, OPT_Wmultiple_parameter_fwd_decl_lists,
+ "more than one list of forward declarations of parameters are
an obsolescent feature");
+ if (pedantic && !current_scope->had_forward_parm_decls)
+ pedwarn (input_location, OPT_Wpedantic,
+ "ISO C forbids forward parameter declarations");
+
+ current_scope->had_forward_parm_decls = true;
for (b = current_scope->bindings; b; b = b->prev)
if (TREE_CODE (b->decl) == PARM_DECL)
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 2922d9e9839..2b92dee5cfd 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -675,7 +675,7 @@ declaration}, and it serves the purpose of making the name
@code{len}
known when the declaration of @code{data} is parsed.
You can write any number of such parameter forward declarations in the
-parameter list. They can be separated by commas or semicolons, but the
+parameter list. They can be separated by commas, and the
last one must end with a semicolon, which is followed by the ``real''
parameter declarations. Each forward declaration must match a ``real''
declaration in parameter name and data type. ISO C99 does not support
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index d0c13d4a24e..b29d796d5e9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -540,7 +540,9 @@ Objective-C and Objective-C++ Dialects}.
@gccoptlist{-Wbad-function-cast -Wdeprecated-non-prototype -Wfree-labels
-Wmissing-declarations -Wmissing-parameter-name -Wmissing-parameter-type
-Wdeclaration-missing-parameter-type -Wmissing-prototypes
--Wmissing-variable-declarations -Wnested-externs -Wold-style-declaration
+-Wmissing-variable-declarations
+-Wmultiple-parameter-fwd-decl-lists
+-Wnested-externs -Wold-style-declaration
-Wold-style-definition -Wstrict-prototypes -Wtraditional
-Wtraditional-conversion -Wdeclaration-after-statement -Wpointer-sign}
@@ -6682,6 +6684,7 @@ name is still supported, but the newer name is more
descriptive.)
-Wmissing-parameter-name @r{(C/ObjC only)}
-Wmissing-parameter-type @r{(C/ObjC only)}
-Wold-style-declaration @r{(C/ObjC only)}
+-Wmultiple-parameter-fwd-decl-lists @r{(C/ObjC only)}
-Woverride-init @r{(C/ObjC only)}
-Wredundant-move @r{(C++ and Objective-C++ only)}
-Wshift-negative-value @r{(in C++11 to C++17 and in C99 and newer)}
@@ -10535,6 +10538,14 @@ is not considered an old-style definition in C23 mode,
because it is
equivalent to @samp{(void)} in that case, but is considered an
old-style definition for older standards.
+@opindex Wmultiple-parameter-fwd-decl-lists
+@opindex Wno-multiple-parameter-fwd-decl-lists
+@item -Wmultiple-parameter-fwd-decl-lists @r{(C and Objective-C only)}
+Warn if more than one list of forward declarations of parameters
+appears in a function prototype,
+which is an obsolescent feature.
+This warning is also enabled by @option{-Wextra}.
+
@opindex Wdeprecated-non-prototype
@opindex Wno-deprecated-non-prototype
@item -Wdeprecated-non-prototype @r{(C and Objective-C only)}
diff --git a/gcc/testsuite/gcc.dg/Wmultiple-parameter-fwd-decl-lists.c
b/gcc/testsuite/gcc.dg/Wmultiple-parameter-fwd-decl-lists.c
new file mode 100644
index 00000000000..d9baeedc137
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wmultiple-parameter-fwd-decl-lists.c
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+/* { dg-options "-Wmultiple-parameter-fwd-decl-lists } */
+
+void f(int n, int m; int n, int m);
+void g(int n; int m; int n, int m); /* { dg-warning "more than one list of
forward declarations" } */
+void h(int n; int n; int n); /* { dg-warning "more than one list of forward
declarations" } */
--
2.50.1
