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gcc: remove BR2_GCC_ENABLE_TLS option

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The current BR2_GCC_ENABLE_TLS can cause users to make incorrect
choices, and is not very useful. This options allows to decide whether
we pass --enable-tls or --disable-tls to gcc, to enable or disable
support for Thread Local Storage.

Its behavior is:

 - The option is default to "y" but only exists if we're using
   uClibc/NPTL or glibc.

 - When we're using uClibc, the option can be disabled.

So, in practice, this means that currently:

 - TLS support is always on for glibc

 - TLS support is on by default for uClibc/NPTL, but can be disabled in
   the configuration. This is in fact bad and causes the build failure
   reported in bug #7424 (this bug is still reproducible on master)

 - TLS support is always disabled for uClibc/no-thread and
   uClibc/linuxthreads.

 - TLS support is always disabled for musl. This does not cause any
   build failure, but musl can use TLS support, and therefore be more
   efficient. According to
   http://www.openwall.com/lists/musl/2012/10/04/1, "Note that if you've
   been building gcc with --disable-tls, __thread was already working
   but gets emulated (very poorly; it's slow and will abort() if it runs
   out of memory) through libgcc.".

So, this commit completely removes the BR2_GCC_ENABLE_TLS and instead
makes the right choice inside gcc.mk directly:

 - TLS support enabled for glibc, musl and uClibc/NPTL

 - TLS support in other cases, i.e uClibc/no-thread and
   uClibc/linuxthreads.

We have intentionally *not* added the option to
Config.in.legacy. Indeed, the new behavior is *exactly* the same as the
older behavior, with the exception of:

 - People can no longer disable TLS support in uClibc/NPTL, which was
   anyway causing a build failure and therefore was not used.

 - TLS support is now enabled on musl, but people using musl already had
   BR2_GCC_ENABLE_TLS not set, so they wouldn't get the legacy warning.

Fixes bug #7424.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
This commit is contained in:
Thomas Petazzoni 2016-08-30 23:33:28 +02:00
parent 511a161b87
commit 1bd02bc230
2 changed files with 6 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
package/gcc/Config.in.host
View File

@ -154,14 +154,6 @@ config BR2_TOOLCHAIN_BUILDROOT_FORTRAN
Fortran language and you want Fortran libraries to be Fortran language and you want Fortran libraries to be
installed on your target system. installed on your target system.
config BR2_GCC_ENABLE_TLS
bool "Enable compiler tls support" if BR2_TOOLCHAIN_BUILDROOT_UCLIBC
default y
depends on BR2_PTHREADS_NATIVE || BR2_TOOLCHAIN_BUILDROOT_GLIBC
help
Enable the compiler to generate code for accessing
thread local storage variables
config BR2_GCC_ENABLE_LTO config BR2_GCC_ENABLE_LTO
bool "Enable compiler link-time-optimization support" bool "Enable compiler link-time-optimization support"
select BR2_BINUTILS_ENABLE_LTO select BR2_BINUTILS_ENABLE_LTO

9
package/gcc/gcc.mk
View File

@ -133,10 +133,13 @@ ifeq ($(BR2_sparc)$(BR2_sparc64),y)
HOST_GCC_COMMON_CONF_OPTS += --disable-libsanitizer HOST_GCC_COMMON_CONF_OPTS += --disable-libsanitizer
endif endif
ifeq ($(BR2_GCC_ENABLE_TLS),y) # TLS support is not needed on uClibc/no-thread and
HOST_GCC_COMMON_CONF_OPTS += --enable-tls # uClibc/linux-threads, otherwise, for all other situations (glibc,
else # musl and uClibc/NPTL), we need it.
ifeq ($(BR2_TOOLCHAIN_BUILDROOT_UCLIBC)$(BR2_PTHREADS)$(BR2_PTHREADS_NONE),yy)
HOST_GCC_COMMON_CONF_OPTS += --disable-tls HOST_GCC_COMMON_CONF_OPTS += --disable-tls
else
HOST_GCC_COMMON_CONF_OPTS += --enable-tls
endif endif
ifeq ($(BR2_GCC_ENABLE_LTO),y) ifeq ($(BR2_GCC_ENABLE_LTO),y)