shims/super/cc: unset LD_LIBRARY_PATH

[ZhongRuoyu]

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A local ruby build failed while building extensions, with:

*** Following extensions are not compiled:
-test-/file:
  Could not be configured. It will not be installed.
  /tmp/ruby-20240824-893184-ehcnsa/ruby-3.3.4/lib/mkmf.rb:480: The compiler failed to generate an executable file.
  You have to install development tools first.
  Check ext/-test-/file/mkmf.log for more details.
-test-/symbol:
  Could not be configured. It will not be installed.
  /tmp/ruby-20240824-893184-ehcnsa/ruby-3.3.4/lib/mkmf.rb:480: The compiler failed to generate an executable file.
  You have to install development tools first.
  Check ext/-test-/symbol/mkmf.log for more details.
[...]

mkmf.log indicated that the compiler shim failed to load pathname:

LD_LIBRARY_PATH=.:../../.. "gcc-13 -o conftest -I../../../.ext/include/aarch64-linux -I../../.././include -I../../.././ext/-test-/file -I/home/linuxbrew/.linuxbrew/opt/libyaml/include -I/home/linuxbrew/.linuxbrew/opt/openssl@3/include    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wdiv-by-zero -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wpointer-arith -Wwrite-strings -Wold-style-definition -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wmisleading-indentation -Wundef  -fPIC conftest.c  -L. -L../../.. -L/home/linuxbrew/.linuxbrew/opt/libyaml/lib -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/libyaml/lib -L/home/linuxbrew/.linuxbrew/opt/openssl@3/lib -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/openssl@3/lib -L. -fstack-protector-strong -L/home/linuxbrew/.linuxbrew/opt/libyaml/lib  -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/libyaml/lib -L/home/linuxbrew/.linuxbrew/opt/openssl@3/lib  -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/openssl@3/lib -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/linuxbrew/.linuxbrew/Cellar/ruby/3.3.4/lib -L/home/linuxbrew/.linuxbrew/Cellar/ruby/3.3.4/lib -lruby-static -lz -lrt -lrt -ldl -lcrypt -lm -lpthread   -lm -lpthread  -lc"
/home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/shims/linux/super/gcc-13:12:in `require': cannot load such file -- pathname (LoadError)
  from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/shims/linux/super/gcc-13:12:in `<main>'

I believe this was due to ../../.. in LD_LIBRARY_PATH containing libruby.so, causing the Ruby script to load the being-built Ruby library instead of the system/portable one.

[Bo98]

Where does the LD_LIBRARY_PATH come from if we have env filtering?

[Bo98]

Oh right I think I understand now - misread the part that it's how our compiler shim executing Ruby that fails.

[ZhongRuoyu]

It comes from the Ruby build itself, somehow. The gcc-13 shim (which I believe does not have environment filtering) was invoked with LD_LIBRARY_PATH=.:../../...

[Bo98]

Does GNU ld use LD_LIBRARY_PATH itself at all? I wonder if we need to save this env and then re-apply it before invoking the real compiler/linker?

[ZhongRuoyu]

Ah it does seem so: https://sourceware.org/binutils/docs/ld/Options.html

-rpath-link=dir

When additional shared libraries are required, the linker will search directories in the order listed below in order to find them. ...

...
5. For a native linker, search the contents of the environment variable LD_LIBRARY_PATH.

So preserving the variable makes sense. I've pushed an update.

[MikeMcQuaid]

Thanks @ZhongRuoyu, good catch!