https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102803
Bug ID: 102803
Summary: Bug: -no-canonical-prefixes not working
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: driver
Assignee: unassigned at gcc dot gnu.org
Reporter: carlosgalvezp at gmail dot com
Target Milestone: ---
Hi,
GCC has the option "-no-canonical-prefixes" to avoid calling "realpath" on
default include search paths. This is needed when one wants to use GCC in
Bazel:
https://github.com/bazelbuild/bazel/issues/4605#issuecomment-364174051
Now, GCC as downloaded from here:
http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu/pool/main/g/gcc-11/g++-11_11.1.0-1ubuntu1~18.04.1_amd64.deb
does *not* honor the -no-canonical-prefixes flag.
If one unpacks the above .deb file into e.g. /path/to/gcc, and runs gcc from
there like ./usr/bin/gcc-11 with the -no-canonical-prefixes option, then the
default search paths resolve all symlinks and "../", leading to a realpath:
/path/to/gcc# ./usr/bin/gcc-11 -no-canonical-prefixes
-fno-canonical-system-headers -xc++ -E -v -
ignoring nonexistent directory
"./usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11/x86_64-linux-gnu"
ignoring nonexistent directory
"./usr/bin/../lib/gcc/x86_64-linux-gnu/11/include"
ignoring nonexistent directory
"./usr/bin/../lib/gcc/x86_64-linux-gnu/11/include-fixed"
ignoring nonexistent directory
"./usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include"
ignoring duplicate directory "/path/to/gcc/usr/include/c++/11"
ignoring duplicate directory "/path/to/gcc/usr/include/x86_64-linux-gnu/c++/11"
ignoring duplicate directory "/path/to/gcc/usr/include/x86_64-linux-gnu/c++/11"
ignoring duplicate directory "/path/to/gcc/usr/include/c++/11/backward"
ignoring nonexistent directory
"./usr/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11/include"
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"./usr/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11/include-fixed"
ignoring nonexistent directory
"./usr/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include"
ignoring nonexistent directory "/usr/include/x86_64-linux-gnu"
#include "..." search starts here:
#include <...> search starts here:
/path/to/gcc/usr/include/c++/11
/path/to/gcc/usr/include/x86_64-linux-gnu/c++/11
/path/to/gcc/usr/include/c++/11/backward
/usr/local/include
/usr/include
I.e. the default search paths are:
/path/to/gcc/usr/include/c++/11
/path/to/gcc/usr/include/x86_64-linux-gnu/c++/11
/path/to/gcc/usr/include/c++/11/backward
Instead of:
./usr/bin/../include/c++/11
This happens also on GCC 7.
Why is this happening? Can it be solved? This prevents GCC from being used in
Bazel in a sandboxed way (i.e. without having GCC installed in the system).
