diff mbox

Document use of CC and CFLAGS in more detail (bug 20980, bug 21234)

Message ID alpine.DEB.2.20.1802012037260.13065@digraph.polyomino.org.uk
State New
Headers show

Commit Message

Joseph Myers Feb. 1, 2018, 8:37 p.m. UTC
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

Joseph Myers Feb. 6, 2018, 6:03 p.m. UTC | #1
Ping.  This patch 
<https://sourceware.org/ml/libc-alpha/2018-02/msg00037.html> is pending 
review.
Joseph Myers Feb. 12, 2018, 4:30 p.m. UTC | #2
Ping^2.  This patch 
<https://sourceware.org/ml/libc-alpha/2018-02/msg00037.html> is pending 
review.
Carlos O'Donell Feb. 15, 2018, 11:03 p.m. UTC | #3
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
>
Rical Jasan Feb. 16, 2018, 4:50 a.m. UTC | #4
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
Joseph Myers Feb. 16, 2018, 1:53 p.m. UTC | #5
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.
diff mbox

Patch

diff --git a/INSTALL b/INSTALL
index 68b9252..912ff63 100644
--- a/INSTALL
+++ b/INSTALL
@@ -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
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
+@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