Bootstrapped GCC is using incorrect search paths

Question

I'm attempting to build GCC 10.5 for an older version of QNX on an x86 platform in an Ubuntu 20.04 x86_64 environment. I downloaded the gcc-10.5.0.tar.xz file from GNU's FTP server and ran the following commands:

tar -xvf gcc-10.5.0.tar.xz
cd gcc-10.5.0
./contrib/download_prerequisites
cd ..
mkdir bin-qnx63-i386
cd bin-qnx63-i386
./../gcc-10.5.0/configure $(options)
make

These are the current options in $(options):

• --host=x86_64-pc-linux-gnu
• --target=i386-pc-nto-qnx6.3.0
• --prefix=/usr/local/nyab
• --program-prefix=nyab-
• --disable-multilib
• --enable-threads=posix
• --enable-tls
• --enable-version-specific-runtime-libs
• --enable-languages=c,c++
• --disable-libada
• --disable-libgm2
• --enable-default-pie
• --enable-werror
• --enable-checking
• --enable-valgrind-annotations
• --with-sysroot=/opt/qnx630/target/qnx6

In addition, I've copied ar, as, ld and ranlib from the SDK to /usr/local/nyab/i386-pc-nto-qnx6.3.0/bin as directed here. After an initial failed run, I copied the CRT libraries from the SDK to /usr/local/nyab/i386-pc-nto-qnx6.3.0/lib as that appeared to be needed as well.

This setup seems to work until I get to the i386-pc-nto-qnx6.3.0/libstdc++-v3 directory where it fails. Looking at config.log the issue seems to stem from the following line:

/usr/local/nyab/i386-pc-nto-qnx6.3.0/bin/ld: cannot open /opt/qnx630/target/qnx6x86/lib/crtbegin.o: No such file or directory

The correct path is /opt/qnx630/target/qnx6/x86/lib.

I've attempted to modify the --with-sysroot option to include trailing slashes, but that seems to have no effect. Next, I created a small C file:

#include <stdio.h>

int main(void) {
    printf("Hello, world!\n");
    return 0;
}

I passed it to the compiler using the flags of the failing command plus the flag to spit out additional information (formatted for StackOverflow):

/home/nyab/gcc/bin-qnx63-i386/./gcc/xgcc -B/home/nyab/gcc/bin-qnx63-i386/./gcc/ \
    -B/usr/local/nyab/i386-pc-nto-qnx6.3.0/bin/ \
    -B/usr/local/nyab/i386-pc-nto-qnx6.3.0/lib/ \
    -isystem /usr/local/nyab/i386-pc-nto-qnx6.3.0/include \
    -isystem /usr/local/nyab/i386-pc-nto-qnx6.3.0/sys-include \
    -v -o /tmp/test -g -O2 /tmp/test.c

And found that GCC is creating the incorrect paths (newlines added for the incorrect paths):

...
COLLECT_GCC_OPTIONS='-B' '/home/nyab/gcc/bin-qnx63-i386/./gcc/' '-B' '/usr/local/nyab/i386-pc-nto-qnx6.3.0/bin/' '-B' '/usr/local/nyab/i386-pc-nto-qnx6.3.0/lib/' '-isystem' '/usr/local/nyab/i386-pc-nto-qnx6.3.0/include' '-isystem' '/usr/local/nyab/i386-pc-nto-qnx6.3.0/sys-include' '-v' '-o' '/tmp/test' '-g' '-O2' '-mtune=generic' '-march=pentiumpro'
 /home/nyab/gcc/bin-qnx63-i386/./gcc/collect2 -V -Y P,

/opt/qnx630/target/qnx6x86/lib

 -Qy -m i386nto --dynamic-linker /usr/lib/ldqnx.so.2 -o /tmp/test /usr/local/nyab/i386-pc-nto-qnx6.3.0/lib/crt1.o /usr/local/nyab/i386-pc-nto-qnx6.3.0/lib/crti.o

/opt/qnx630/target/qnx6x86/lib/crtbegin.o

 -L/home/nyab/gcc/bin-qnx63-i386/./gcc -L/usr/local/nyab/i386-pc-nto-qnx6.3.0/bin -L/usr/local/nyab/i386-pc-nto-qnx6.3.0/lib /tmp/ccb1wUOU.o -lgcc -lc -lgcc /usr/local/nyab/i386-pc-nto-qnx6.3.0/lib/crtend.o /usr/local/nyab/i386-pc-nto-qnx6.3.0/lib/crtn.o
...

I have confirmed crtbegin.o is in /usr/local/nyab/i386-pc-nto-qnx6.3.0/lib although it was copied from /opt/qnx630/target/qnx6/x86/lib. Does anyone know where I went wrong or what to try next?

Answer 1

Short answer

Modify SYSROOT_SUFFIX_SPEC in <src-dir>/gcc/config/i386/nto.h to /86.

Long answer

GCC uses spec files to determine how to call itself and other programs with their appropriate command line arguments. Thorough investigation of <src-dir>/gcc/gcc.c will show you how these files are created or read in to the program. Since we fail during linker invocation, the LINK_SPEC definition matters here. For this QNX build, its found in <src-dir>/gcc/config/i386/nto.h. The two lines that matter are:

...
   %{!YP,*:%{p:-Y P,%R/lib} \
    %{!p:-Y P,%R/lib}} \
...

The spec language reference linked earlier says %R is "the concatenation of target_system_root and target_sysroot_suffix." The target_sysroot_suffix is actually defined in the nto.h file under the SYSROOT_SUFFIX_SPEC preprocessor macro. Cross referencing this definition with other definitions in mti-linux.h and st.h, the specification in nto.h is missing the forward slash at the beginning. Changing the value from x86 to /x86 will get you past this issue.