Document use of CC and CFLAGS in more detail (bug 20980, bug 21234)
Commit Message
There are some bug reports from people setting CFLAGS not including a
-O option and then being confused when the build fails. This patch
addresses this by documenting the proper use of CC and CFLAGS in more
detail - saying what options should go where and specifying the
requirement to compile with optimization.
The previous text incorrectly used @var markup with CC and CFLAGS.
The correct markup for environment variables is @env, but it's also
the case that passing such variables explicitly on the configure
command line is preferred to passing them in the environment, so this
patch changes the documentation to describe passing them on the
command line (and uses @code).
In many cases putting options in the wrong place may in fact work, but
I believe what I've specified is the correct rule for which options to
put where.
2018-02-01 Joseph Myers <joseph@codesourcery.com>
[BZ #20980]
[BZ #21234]
* manual/install.texi (Configuring and compiling): Describe
passing CC and CFLAGS on configure command line, not as
environment variables. Use @code markup on those variables.
Specify what options go in CC and what go in CFLAGS. Note the
requirement to compile with optimization.
* INSTALL: Regenerated.
Comments
Ping. This patch
<https://sourceware.org/ml/libc-alpha/2018-02/msg00037.html> is pending
review.
Ping^2. This patch
<https://sourceware.org/ml/libc-alpha/2018-02/msg00037.html> is pending
review.
On 02/01/2018 12:37 PM, Joseph Myers wrote:
> There are some bug reports from people setting CFLAGS not including a
> -O option and then being confused when the build fails. This patch
> addresses this by documenting the proper use of CC and CFLAGS in more
> detail - saying what options should go where and specifying the
> requirement to compile with optimization.
>
> The previous text incorrectly used @var markup with CC and CFLAGS.
> The correct markup for environment variables is @env, but it's also
> the case that passing such variables explicitly on the configure
> command line is preferred to passing them in the environment, so this
> patch changes the documentation to describe passing them on the
> command line (and uses @code).
>
> In many cases putting options in the wrong place may in fact work, but
> I believe what I've specified is the correct rule for which options to
> put where.
>
> 2018-02-01 Joseph Myers <joseph@codesourcery.com>
>
> [BZ #20980]
> [BZ #21234]
> * manual/install.texi (Configuring and compiling): Describe
> passing CC and CFLAGS on configure command line, not as
> environment variables. Use @code markup on those variables.
> Specify what options go in CC and what go in CFLAGS. Note the
> requirement to compile with optimization.
> * INSTALL: Regenerated.
OK with additions suggested below.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> --- a/manual/install.texi
> +++ b/manual/install.texi
> @@ -59,10 +59,17 @@ but the normal setting to install as the standard system library is
> @samp{--prefix=/usr} for @gnulinuxsystems{} and @samp{--prefix=} (an
> empty prefix) for @gnuhurdsystems{}.
>
> -It may also be useful to set the @var{CC} and @var{CFLAGS} variables in
> -the environment when running @code{configure}. @var{CC} selects the C
> -compiler that will be used, and @var{CFLAGS} sets optimization options
> -for the compiler.
> +It may also be useful to pass @samp{CC=@var{compiler}} and
> +@code{CFLAGS=@var{flags}} arguments to @code{configure}. @code{CC}
> +selects the C compiler that will be used, and @code{CFLAGS} sets
> +optimization options for the compiler. Any compiler options required
> +for all compilations, such as options selecting an ABI or a processor
> +for which to generate code, should be included in @code{CC}. Options
> +that may be overridden by the @glibcadj{} build system for particular
> +files, such as for optimization and debugging, should go in
> +@code{CFLAGS}.
Suggest adding:
@smallexample
$ ../glibc-@var{version}/configure CC="gcc -m32" CFLAGS="-O3"
@end smallexample
Just to make this perfectly clear.
The default value of @code{CFLAGS} is @samp{-g -O2},
> +and @theglibc{} cannot be compiled without optimization, so if
> +@code{CFLAGS} is specified it must enable optimization.
OK.
>
> The following list describes all of the available options for
> @code{configure}:
> @@ -241,7 +248,7 @@ if @code{configure} guesses your machine as @code{i686-pc-linux-gnu} but
> you want to compile a library for 586es, give
> @samp{--host=i586-pc-linux-gnu} or just @samp{--host=i586-linux} and add
> the appropriate compiler flags (@samp{-mcpu=i586} will do the trick) to
> -@var{CFLAGS}.
> +@code{CC}.
OK.
>
> If you specify just @samp{--build}, @code{configure} will get confused.
>
> @@ -339,8 +346,8 @@ It is easy to configure @theglibc{} for cross-compilation by
> setting a few variables in @file{configparms}. Set @code{CC} to the
> cross-compiler for the target you configured the library for; it is
> important to use this same @code{CC} value when running
> -@code{configure}, like this: @samp{CC=@var{target}-gcc configure
> -@var{target}}. Set @code{BUILD_CC} to the compiler to use for programs
> +@code{configure}, like this: @samp{configure @var{target}
> +CC=@var{target}-gcc}. Set @code{BUILD_CC} to the compiler to use for programs
OK.
> run on the build system as part of compiling the library. You may need to
> set @code{AR} to cross-compiling versions of @code{ar}
> if the native tools are not configured to work with
>
On 02/01/2018 12:37 PM, Joseph Myers wrote:
...
> diff --git a/manual/install.texi b/manual/install.texi
> index efcd986..5cf8e16 100644
> --- a/manual/install.texi
> +++ b/manual/install.texi
> @@ -59,10 +59,17 @@ but the normal setting to install as the standard system library is
> @samp{--prefix=/usr} for @gnulinuxsystems{} and @samp{--prefix=} (an
> empty prefix) for @gnuhurdsystems{}.
>
> -It may also be useful to set the @var{CC} and @var{CFLAGS} variables in
> -the environment when running @code{configure}. @var{CC} selects the C
> -compiler that will be used, and @var{CFLAGS} sets optimization options
> -for the compiler.
> +It may also be useful to pass @samp{CC=@var{compiler}} and
Is this a rogue @samp here, or was that intentional (everywhere else is
@code)?
Otherwise, I think this patch achieves the goal of more explicitly
documenting expected usage of CC and CFLAGS. (I see it's been
committed, but hopefully an additional ACK doesn't hurt. :)
Rical
On Fri, 16 Feb 2018, Rical Jasan wrote:
> On 02/01/2018 12:37 PM, Joseph Myers wrote:
> ...
> > diff --git a/manual/install.texi b/manual/install.texi
> > index efcd986..5cf8e16 100644
> > --- a/manual/install.texi
> > +++ b/manual/install.texi
> > @@ -59,10 +59,17 @@ but the normal setting to install as the standard system library is
> > @samp{--prefix=/usr} for @gnulinuxsystems{} and @samp{--prefix=} (an
> > empty prefix) for @gnuhurdsystems{}.
> >
> > -It may also be useful to set the @var{CC} and @var{CFLAGS} variables in
> > -the environment when running @code{configure}. @var{CC} selects the C
> > -compiler that will be used, and @var{CFLAGS} sets optimization options
> > -for the compiler.
> > +It may also be useful to pass @samp{CC=@var{compiler}} and
>
> Is this a rogue @samp here, or was that intentional (everywhere else is
> @code)?
It's intentional, in that it matches (for example) the
@samp{--prefix=/usr} quoted above.
@@ -36,9 +36,16 @@ normal setting to install as the standard system library is
'--prefix=/usr' for GNU/Linux systems and '--prefix=' (an empty prefix)
for GNU/Hurd systems.
- It may also be useful to set the CC and CFLAGS variables in the
-environment when running 'configure'. CC selects the C compiler that
-will be used, and CFLAGS sets optimization options for the compiler.
+ It may also be useful to pass 'CC=COMPILER' and 'CFLAGS=FLAGS'
+arguments to 'configure'. 'CC' selects the C compiler that will be
+used, and 'CFLAGS' sets optimization options for the compiler. Any
+compiler options required for all compilations, such as options
+selecting an ABI or a processor for which to generate code, should be
+included in 'CC'. Options that may be overridden by the GNU C Library
+build system for particular files, such as for optimization and
+debugging, should go in 'CFLAGS'. The default value of 'CFLAGS' is '-g
+-O2', and the GNU C Library cannot be compiled without optimization, so
+if 'CFLAGS' is specified it must enable optimization.
The following list describes all of the available options for
'configure':
@@ -210,7 +217,7 @@ will be used, and CFLAGS sets optimization options for the compiler.
but you want to compile a library for 586es, give
'--host=i586-pc-linux-gnu' or just '--host=i586-linux' and add the
appropriate compiler flags ('-mcpu=i586' will do the trick) to
- CFLAGS.
+ 'CC'.
If you specify just '--build', 'configure' will get confused.
@@ -304,7 +311,7 @@ makefiles.
setting a few variables in 'configparms'. Set 'CC' to the
cross-compiler for the target you configured the library for; it is
important to use this same 'CC' value when running 'configure', like
-this: 'CC=TARGET-gcc configure TARGET'. Set 'BUILD_CC' to the compiler
+this: 'configure TARGET CC=TARGET-gcc'. Set 'BUILD_CC' to the compiler
to use for programs run on the build system as part of compiling the
library. You may need to set 'AR' to cross-compiling versions of 'ar'
if the native tools are not configured to work with object files for the
@@ -59,10 +59,17 @@ but the normal setting to install as the standard system library is
@samp{--prefix=/usr} for @gnulinuxsystems{} and @samp{--prefix=} (an
empty prefix) for @gnuhurdsystems{}.
-It may also be useful to set the @var{CC} and @var{CFLAGS} variables in
-the environment when running @code{configure}. @var{CC} selects the C
-compiler that will be used, and @var{CFLAGS} sets optimization options
-for the compiler.
+It may also be useful to pass @samp{CC=@var{compiler}} and
+@code{CFLAGS=@var{flags}} arguments to @code{configure}. @code{CC}
+selects the C compiler that will be used, and @code{CFLAGS} sets
+optimization options for the compiler. Any compiler options required
+for all compilations, such as options selecting an ABI or a processor
+for which to generate code, should be included in @code{CC}. Options
+that may be overridden by the @glibcadj{} build system for particular
+files, such as for optimization and debugging, should go in
+@code{CFLAGS}. The default value of @code{CFLAGS} is @samp{-g -O2},
+and @theglibc{} cannot be compiled without optimization, so if
+@code{CFLAGS} is specified it must enable optimization.
The following list describes all of the available options for
@code{configure}:
@@ -241,7 +248,7 @@ if @code{configure} guesses your machine as @code{i686-pc-linux-gnu} but
you want to compile a library for 586es, give
@samp{--host=i586-pc-linux-gnu} or just @samp{--host=i586-linux} and add
the appropriate compiler flags (@samp{-mcpu=i586} will do the trick) to
-@var{CFLAGS}.
+@code{CC}.
If you specify just @samp{--build}, @code{configure} will get confused.
@@ -339,8 +346,8 @@ It is easy to configure @theglibc{} for cross-compilation by
setting a few variables in @file{configparms}. Set @code{CC} to the
cross-compiler for the target you configured the library for; it is
important to use this same @code{CC} value when running
-@code{configure}, like this: @samp{CC=@var{target}-gcc configure
-@var{target}}. Set @code{BUILD_CC} to the compiler to use for programs
+@code{configure}, like this: @samp{configure @var{target}
+CC=@var{target}-gcc}. Set @code{BUILD_CC} to the compiler to use for programs
run on the build system as part of compiling the library. You may need to
set @code{AR} to cross-compiling versions of @code{ar}
if the native tools are not configured to work with