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toolchain-external: update comments

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[Peter: drop extra # as pointed out by Baruch Siach]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Thomas Petazzoni 2013-11-07 00:08:02 +01:00 committed by Peter Korsgaard
parent 620d85b310
commit b07c2affc9
1 changed files with 24 additions and 18 deletions
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42
toolchain/toolchain-external/toolchain-external.mk
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@ -13,14 +13,21 @@
#
# * Toolchains generated by Crosstool-NG
# * Toolchains generated by Buildroot
# * ARM, MIPS and PowerPC toolchains made available by
# Codesourcery. For the MIPS toolchain, the -muclibc variant isn't
# supported yet, only the default glibc-based variant is.
# * Toolchains provided by Linaro for the ARM and AArch64
# architectures
# * Sourcery CodeBench toolchains (from Mentor Graphics) for the ARM,
# MIPS, PowerPC, x86, x86_64 and NIOS 2 architectures. For the MIPS
# toolchain, the -muclibc variant isn't supported yet, only the
# default glibc-based variant is.
# * Analog Devices toolchains for the Blackfin architecture
# * Xilinx toolchains for the Microblaze architecture
#
# The basic principle is the following
#
# 1. If the toolchain is not pre-installed, download and extract it
# in $(TOOLCHAIN_EXTERNAL_INSTALL_DIR).
# in $(TOOLCHAIN_EXTERNAL_INSTALL_DIR). Otherwise,
# $(TOOLCHAIN_EXTERNAL_INSTALL_DIR) points to were the toolchain has
# already been installed by the user.
#
# 2. For all external toolchains, perform some checks on the
# conformity between the toolchain configuration described in the
@ -85,22 +92,21 @@ LIB_EXTERNAL_LIBS+=$(call qstrip,$(BR2_TOOLCHAIN_EXTRA_EXTERNAL_LIBS))
# Details about sysroot directory selection.
#
# To find the sysroot directory:
# To find the sysroot directory, we use the trick of looking for the
# 'libc.a' file with the -print-file-name gcc option, and then
# mangling the path to find the base directory of the sysroot.
#
# * We first try the -print-sysroot option, available in gcc 4.4.x
# and in some Codesourcery toolchains.
# Note that we do not use the -print-sysroot option, because it is
# only available since gcc 4.4.x, and we still support 4.2.x (for
# AVR32) and 4.3.x.
#
# * If this option is not available, we fallback to the value of
# --with-sysroot as visible in CROSS-gcc -v.
#
# When doing those tests, we don't pass any option to gcc that could
# select a multilib variant (such as -march) as we want the "main"
# sysroot, which contains all variants of the C library in the case of
# multilib toolchains. We use the TARGET_CC_NO_SYSROOT variable, which
# is the path of the cross-compiler, without the
# --sysroot=$(STAGING_DIR), since what we want to find is the location
# of the original toolchain sysroot. This "main" sysroot directory is
# stored in SYSROOT_DIR.
# When doing this, we don't pass any option to gcc that could select a
# multilib variant (such as -march) as we want the "main" sysroot,
# which contains all variants of the C library in the case of multilib
# toolchains. We use the TARGET_CC_NO_SYSROOT variable, which is the
# path of the cross-compiler, without the --sysroot=$(STAGING_DIR),
# since what we want to find is the location of the original toolchain
# sysroot. This "main" sysroot directory is stored in SYSROOT_DIR.
#
# Then, multilib toolchains are a little bit more complicated, since
# they in fact have multiple sysroots, one for each variant supported