path: root/INSTALL
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authorJoseph Myers <joseph@codesourcery.com>2018-02-15 23:48:47 +0000
committerJoseph Myers <joseph@codesourcery.com>2018-02-15 23:48:47 +0000
commitdb9881ecd7e7278af3e6bb252a0b3015e275d7bd (patch)
tree18ae8d859278144438c5e0cc960e2c49da87b1b5 /INSTALL
parent3785b31c16a507538a9f67f20c75b8a1dfe9939a (diff)
Document use of CC and CFLAGS in more detail (bug 20980, bug 21234).
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. [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.
Diffstat (limited to 'INSTALL')
1 files changed, 14 insertions, 5 deletions
diff --git a/INSTALL b/INSTALL
index 64dec3473e1..052b1b6f890 100644
@@ -36,9 +36,18 @@ 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. For example:
+ $ ../glibc-VERSION/configure CC="gcc -m32" CFLAGS="-O3"
The following list describes all of the available options for
@@ -210,7 +219,7 @@ 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
+ 'CC'.
If you specify just '--build', 'configure' will get confused.
@@ -304,7 +313,7 @@ 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