* [Buildroot] Where the cross-compiler gets shared stuff
@ 2019-11-22 8:00 Frederick Gotham
2019-11-22 9:37 ` Thomas Preston
0 siblings, 1 reply; 2+ messages in thread
From: Frederick Gotham @ 2019-11-22 8:00 UTC (permalink / raw)
To: buildroot
Typically, when a cross-compiler is installed properly on a computer, do you
need to explicitly invoke it with "--sysroot=/opt/targetfs", or is this
parameter already implied if the cross-compiler is properly installed?
Right now I'm working on an embedded Linux project, and I'm using Buildroot
to produce a minimalistic Linux installation with only the programs and
libraries I need.
I see that some 3rd party packages invoke the correct cross-compiler but they
don't give the "--sysroot" parameter.
For example, if we start off with the following native compilation command:
gcc main.c -o prog
Then a correct cross-compilation would be:
CC = /opt/project/build/output/host/bin/x86_64-buildroot-linux-gnu-gcc
SYSROOT = /opt/project/build/output/host/x86_64-buildroot-linux-
gnu/sysroot
$(CC) --sysroot=$(SYSROOT) main.c -o prog
I see however that some packages are leaving out the sysroot parameter, and
so they're just doing:
$(CC) main.c -o prog
This predictably fails if the host and the target have different CPU's, for
example if my office PC is x86_64 and my target is embedded Linux ARM
aarch64.
On my current project though, the host and the target have the same CPU, and
so if you leave out the "--sysroot" parameter then the program ends up
linking with shared libraries installed on the host. Sometimes this happens
without any compiler warning or error!
So how are cross-compilers supposed to work? If they are installed properly,
do you need to give them the "--sysroot" parameter?
Note that I'm prefering the use of "--sysroot" instead of using the following
two options: -I$(STAGING_DIR)/usr/include -L$(STAGING_DIR)/usr/lib.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Buildroot] Where the cross-compiler gets shared stuff
2019-11-22 8:00 [Buildroot] Where the cross-compiler gets shared stuff Frederick Gotham
@ 2019-11-22 9:37 ` Thomas Preston
0 siblings, 0 replies; 2+ messages in thread
From: Thomas Preston @ 2019-11-22 9:37 UTC (permalink / raw)
To: buildroot
On 22/11/2019 08:00, Frederick Gotham wrote:
> So how are cross-compilers supposed to work? If they are installed properly,
> do you need to give them the "--sysroot" parameter?
Check out toolchain/toolchain-wrapper.c, which hardcodes a number of toolchain
arguments (including --sysroot). Cross compiler binaries are accessed via
symlinks in $(HOST_DIR)/bin, some of which go through toolchain-wrapper.
$ ls -l output/host/bin/sparc-linux-*
lrwxrwxrwx 1 tpreston tpreston 46 Nov 21 11:18 output/host/bin/sparc-linux-addr2line -> ../opt/ext-toolchain/bin/sparc-linux-addr2line
lrwxrwxrwx 1 tpreston tpreston 39 Nov 21 11:18 output/host/bin/sparc-linux-ar -> ../opt/ext-toolchain/bin/sparc-linux-ar
lrwxrwxrwx 1 tpreston tpreston 39 Nov 21 11:18 output/host/bin/sparc-linux-as -> ../opt/ext-toolchain/bin/sparc-linux-as
lrwxrwxrwx 1 tpreston tpreston 17 Nov 21 11:18 output/host/bin/sparc-linux-c++ -> toolchain-wrapper
lrwxrwxrwx 1 tpreston tpreston 48 Nov 21 11:18 output/host/bin/sparc-linux-c++.br_real -> ../opt/ext-toolchain/bin/sparc-linux-c++.br_real
lrwxrwxrwx 1 tpreston tpreston 17 Nov 21 11:18 output/host/bin/sparc-linux-cc -> toolchain-wrapper
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-11-22 8:00 [Buildroot] Where the cross-compiler gets shared stuff Frederick Gotham
2019-11-22 9:37 ` Thomas Preston
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