Hi Joseph,

Joseph Myers <joseph@codesourcery.com> skribis:

> On Thu, 8 Jul 2021, Ludovic Courtès via Libc-alpha wrote:
>
>> > Hmm.  Why doesn't '$CC -print-prog-name=objcopy' result in the right
>> > command name?
>> 
>> Is it supposed to?  Looking at gcc/gcc.c:find_a_file, I’m not sure.
>> For me it prints ‘objcopy’, and when I run:
>> 
>>   strace aarch64-linux-gnu-gcc -print-prog-name=objcopy
>> 
>> … I only see it look for ‘objcopy’, not ‘aarch64-linux-gnu-objcopy’.
>
> I'd expect it to look for objcopy in $exec_prefix/$target/bin (binutils 
> installs it as objcopy in that directory and as $target-objcopy in 
> $exec_prefix/bin, see TOOL_PROGS in binutils/Makefile.am).  (That path may 
> well in turn be computed via GCC's libexecsubdir, I see output such as 
> /scratch/jmyers/glibc-bot/install/compilers/aarch64-linux-gnu/lib/gcc/aarch64-glibc-linux-gnu/12.0.0/../../../../aarch64-glibc-linux-gnu/bin/objcopy.)

Oh, got it.  That only works when GCC and Binutils are installed in the
same prefix, then.

In Guix, each package is installed in its own prefix.  The cross
Binutils has $exec_prefix/$target/bin as you write:

--8<---------------cut here---------------start------------->8---
$ find /gnu/store/aj1zbw51fvngxrl1r2g6xcxfnlkshr82-binutils-cross-aarch64-linux-gnu-2.34/ -name objdump
/gnu/store/aj1zbw51fvngxrl1r2g6xcxfnlkshr82-binutils-cross-aarch64-linux-gnu-2.34/aarch64-linux-gnu/bin/objdump
--8<---------------cut here---------------end--------------->8---

… but GCC is instead looking for it in its own prefix:

--8<---------------cut here---------------start------------->8---
$ strace -e stat aarch64-linux-gnu-gcc -print-prog-name=objdump
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/tls/haswell/x86_64", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/tls/haswell", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/tls/x86_64", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/tls", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/haswell/x86_64", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/haswell", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/x86_64", 0x7ffc8fcfb630) = -1 ENOENT (No such file or directory)
stat("/gnu/store/1m16gz0q4v4j10k52i5q641sz6lvdwha-gcc-cross-aarch64-linux-gnu-7.5.0/bin/aarch64-linux-gnu-gcc", {st_mode=S_IFREG|0555, st_size=997752, ...}) = 0
stat("/gnu/store/1m16gz0q4v4j10k52i5q641sz6lvdwha-gcc-cross-aarch64-linux-gnu-7.5.0/bin/aarch64-linux-gnu-gcc", {st_mode=S_IFREG|0555, st_size=997752, ...}) = 0
stat("/gnu/store/1m16gz0q4v4j10k52i5q641sz6lvdwha-gcc-cross-aarch64-linux-gnu-7.5.0/libexec/gcc/aarch64-linux-gnu/7.5.0/lto-wrapper", {st_mode=S_IFREG|0555, st_size=909104, ...}) = 0
stat("/gnu/store/1m16gz0q4v4j10k52i5q641sz6lvdwha-gcc-cross-aarch64-linux-gnu-7.5.0/libexec/gcc/aarch64-linux-gnu/7.5.0/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
stat("/gnu/store/1m16gz0q4v4j10k52i5q641sz6lvdwha-gcc-cross-aarch64-linux-gnu-7.5.0/libexec/gcc/aarch64-linux-gnu/7.5.0/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
stat("/gnu/store/1m16gz0q4v4j10k52i5q641sz6lvdwha-gcc-cross-aarch64-linux-gnu-7.5.0/libexec/gcc/aarch64-linux-gnu/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
stat("/gnu/store/029zph27cyn3wvbxmlqh2xqrnk3h3323-gcc-cross-aarch64-linux-gnu-7.5.0-lib/lib/gcc/aarch64-linux-gnu/7.5.0/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
stat("/gnu/store/029zph27cyn3wvbxmlqh2xqrnk3h3323-gcc-cross-aarch64-linux-gnu-7.5.0-lib/lib/gcc/aarch64-linux-gnu/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
stat("/gnu/store/029zph27cyn3wvbxmlqh2xqrnk3h3323-gcc-cross-aarch64-linux-gnu-7.5.0-lib/lib/gcc/aarch64-linux-gnu/7.5.0/../../../../aarch64-linux-gnu/bin/aarch64-linux-gnu/7.5.0/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
stat("/gnu/store/029zph27cyn3wvbxmlqh2xqrnk3h3323-gcc-cross-aarch64-linux-gnu-7.5.0-lib/lib/gcc/aarch64-linux-gnu/7.5.0/../../../../aarch64-linux-gnu/bin/objdump", 0x7ffc8fcfc110) = -1 ENOENT (No such file or directory)
objdump
+++ exited with 0 +++
--8<---------------cut here---------------end--------------->8---

… which fails.

> I'd expect the code to work both before and after the patch.  If there is 
> some advantage to the change proposed in the patch, it would be a good 
> idea for the commit message to explain in more detail the circumstances 
> when the objcopy in $exec_prefix/$target/bin isn't found.

I reworded the commit log of the two patches (attached).

Let me know what you think.

Thanks,
Ludo’.