Re: RFC: Use -Wall -Wextra

Daniel Jacobowitz
2007-01-03T19:12:42Z

On Sat, Dec 30, 2006 at 11:00:34AM -0500, Daniel Jacobowitz wrote:
> Anyway, let's go with -Wall; that's still an improvement over the
> present state and fixes the annoying -Wuninitialized warnings. I'll
> commit my saved up warning fixes, and then post a patch to do this.

Here's what I have just tested on x86_64-pc-linux-gnu. This is a much
more conservative patch than my previous one. It may still break other
targets, especially native ones, with -Werror; I'll be happy to help
fix any breakage if the fixes aren't apparent.

OK to commit?

--
Daniel Jacobowitz
CodeSourcery

2007-01-03 Daniel Jacobowitz <dan@codesourcery.com>

* configure.ac (build_warnings): Use -Wall and
-Wdeclaration-after-statement.
* configure: Regenerated.

2007-01-03 Daniel Jacobowitz <dan@codesourcery.com>

* doc/gdbint.texinfo (Compiler Warnings): Update for -Wall use.

Index: configure.ac
===================================================================
RCS file: /cvs/src/src/gdb/configure.ac,v
retrieving revision 1.37
diff -u -p -r1.37 configure.ac
--- configure.ac 31 Dec 2006 20:20:13 -0000 1.37
+++ configure.ac 3 Jan 2007 19:09:53 -0000
@@ -1138,32 +1138,15 @@ if test "${ERROR_ON_WARNING}" = yes ; th
WERROR_CFLAGS="-Werror"
fi

-# NOTE: Don't add -Wall or -Wunused, they both include
-# -Wunused-parameter which reports bogus warnings.
-# NOTE: If you add to this list, remember to update
+# The entries after -Wno-pointer-sign are disabled warnings which may
+# be enabled in the future, which can not currently be used to build
+# GDB.
+# NOTE: If you change this list, remember to update
# gdb/doc/gdbint.texinfo.
-build_warnings="-Wimplicit -Wreturn-type -Wcomment -Wtrigraphs \
--Wformat -Wparentheses -Wpointer-arith -Wformat-nonliteral \
--Wunused-label -Wunused-function -Wno-pointer-sign"
-
-# GCC supports -Wuninitialized only with -O or -On, n != 0.
-if test x${CFLAGS+set} = xset; then
- case "${CFLAGS}" in
- *"-O0"* ) ;;
- *"-O"* )
- build_warnings="${build_warnings} -Wuninitialized"
- ;;
- esac
-else
- build_warnings="${build_warnings} -Wuninitialized"
-fi
+build_warnings="-Wall -Wdeclaration-after-statement -Wpointer-arith \
+-Wformat-nonliteral -Wno-pointer-sign \
+-Wno-unused -Wno-switch"

-# Up for debate: -Wswitch -Wcomment -trigraphs -Wtrigraphs
-# -Wunused-function -Wunused-variable -Wunused-value
-# -Wchar-subscripts -Wtraditional -Wshadow -Wcast-qual
-# -Wcast-align -Wwrite-strings -Wconversion -Wstrict-prototypes
-# -Wmissing-prototypes -Wmissing-declarations -Wredundant-decls
-# -Woverloaded-virtual -Winline -Werror"
AC_ARG_ENABLE(build-warnings,
[ --enable-build-warnings Enable build-time compiler warnings if gcc is used],
[case "${enableval}" in
@@ -1208,7 +1191,7 @@ then
CFLAGS="$saved_CFLAGS"
esac
done
- AC_MSG_RESULT(${WARN_CFLAGS}${WERROR_CFLAGS})
+ AC_MSG_RESULT(${WARN_CFLAGS} ${WERROR_CFLAGS})
fi
AC_SUBST(WARN_CFLAGS)
AC_SUBST(WERROR_CFLAGS)
Index: doc/gdbint.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdbint.texinfo,v
retrieving revision 1.248
diff -u -p -r1.248 gdbint.texinfo
--- doc/gdbint.texinfo 1 Jan 2007 14:04:18 -0000 1.248
+++ doc/gdbint.texinfo 3 Jan 2007 19:09:55 -0000
@@ -5471,63 +5471,34 @@ errors.}
@subsection Compiler Warnings
@cindex compiler warnings

-With few exceptions, developers should include the configuration option
-@samp{--enable-gdb-build-warnings=,-Werror} when building @value{GDBN}.
-The exceptions are listed in the file @file{gdb/MAINTAINERS}.
+With few exceptions, developers should avoid the configuration option
+@samp{--disable-werror} when building @value{GDBN}. The exceptions
+are listed in the file @file{gdb/MAINTAINERS}. The default, when
+building with @sc{gcc}, is @samp{--enable-werror}.

This option causes @value{GDBN} (when built using GCC) to be compiled
with a carefully selected list of compiler warning flags. Any warnings
-from those flags being treated as errors.
+from those flags are treated as errors.

The current list of warning flags includes:

@table @samp
-@item -Wimplicit
-Since @value{GDBN} coding standard requires all functions to be declared
-using a prototype, the flag has the side effect of ensuring that
-prototyped functions are always visible with out resorting to
-@samp{-Wstrict-prototypes}.
-
-@item -Wreturn-type
-Such code often appears to work except on instruction set architectures
-that use register windows.
+@item -Wall
+Recommended @sc{gcc} warnings.

-@item -Wcomment
+@item -Wdeclaration-after-statement

-@item -Wtrigraphs
-
-@item -Wformat
-@itemx -Wformat-nonliteral
-Since @value{GDBN} uses the @code{format printf} attribute on all
-@code{printf} like functions these check not just @code{printf} calls
-but also calls to functions such as @code{fprintf_unfiltered}.
-
-@item -Wparentheses
-This warning includes uses of the assignment operator within an
-@code{if} statement.
+@sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with
+code, but @sc{gcc} 2.x and @sc{c89} do not.

@item -Wpointer-arith

-@item -Wuninitialized
-
-@item -Wunused-label
-This warning has the additional benefit of detecting the absence of the
-@code{case} reserved word in a switch statement:
-@smallexample
-enum @{ FD_SCHEDULED, NOTHING_SCHEDULED @} sched;
-@dots{}
-switch (sched)
- @{
- case FD_SCHEDULED:
- @dots{};
- break;
- NOTHING_SCHEDULED:
- @dots{};
- break;
- @}
-@end smallexample
-
-@item -Wunused-function
+@item -Wformat-nonliteral
+Non-literal format strings, with a few exceptions, are bugs - they
+might contain unintented user-supplied format specifiers.
+Since @value{GDBN} uses the @code{format printf} attribute on all
+@code{printf} like functions this checks not just @code{printf} calls
+but also calls to functions such as @code{fprintf_unfiltered}.

@item -Wno-pointer-sign
In version 4.0, GCC began warning about pointer argument passing or
@@ -5537,19 +5508,19 @@ carefully between @code{char} and @code{
the @value{GDBN} developers decided correcting these warnings wasn't
worth the time it would take.

-@end table
-
-@emph{Pragmatics: Due to the way that @value{GDBN} is implemented most
-functions have unused parameters. Consequently the warning
-@samp{-Wunused-parameter} is precluded from the list. The macro
+@item -Wno-unused-parameter
+Due to the way that @value{GDBN} is implemented many functions have
+unused parameters. Consequently this warning is avoided. The macro
@code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
-is being used. The options @samp{-Wall} and @samp{-Wunused} are also
-precluded because they both include @samp{-Wunused-parameter}.}
+is being used.
+
+@item -Wno-unused
+@itemx -Wno-switch
+These are warnings which might be useful for @value{GDBN}, but are
+currently too noisy to enable with @samp{-Werror}.

-@emph{Pragmatics: @value{GDBN} has not simply accepted the warnings
-enabled by @samp{-Wall -Werror -W...}. Instead it is selecting warnings
-when and where their benefits can be demonstrated.}
+@end table

@subsection Formatting