Hi Gambit community,

If I understood Gambit's current behavior right, then there's no way to (compile-file "irrelevant.scm" cc-options: "$(SYSTEM EXPLOIT CODE HERE)") .

So Gambit's approach for this argument is similar to a SQL injection attack safety.

This is not a big deal as compile-file probably never is exported to any untrusted user.

However, for symmetry, it makes sense - so spontaneously, while it was a small surprise to me that the conveniency feature of cc-options: \"$(pkg-config --libs libjpeg\")" wouldn't work, on second thought I think the fact that it does not work is rather a feature than a bug, so I'm positive about the current behavior.

Does anyone have an opinion?

Thanks.

2016-07-13 13:56 GMT+08:00 Adam <adam.mlmb@gmail.com>:

Dear Marc,

I'm in a nasty environment where I not can know what exact "-I" and "-l" arguments the C compiler and linker need.

For this reason, I need the pkg-config shell tool to figure it out for me!

It would have seemed logical to me that |compile-file|'s |cc-options:| and |ld-options:| would be evaluated by the system shell by the gambc-cc script, so that this would work:

echo '(print "Hello world\n")' > test.scm

GAMBC_CC_VERBOSE=yes gsc

(compile-file "test.scm"
cc-options: "$(pkg-config --cflags \"libjpeg\")"
ld-options: "$(pkg-config --libs \"libjpeg\")"
)

However, it does not - but instead, the "$(p... strings are passed on verbatim to the C compiler, leading to this output:

gcc [...] -o "test.o1" $(pkg-config --cflags "libjpeg") test.c $(pkg-config --libs "libjpeg")
gcc: error: $(pkg-config: No such file or directory
gcc: error: "libjpeg"): No such file or directory
gcc: error: $(pkg-config: No such file or directory
gcc: error: "libjpeg"): No such file or directory
gcc: error: unrecognized command line option ‘--cflags’
gcc: error: unrecognized command line option ‘--libs’
*** ERROR IN (console)@2.1 -- C compilation or link failed while compiling "test.scm"

I.e. GCC actually gets a "$(pkg-config" argument, a "--cflags" argument and a "\"libjpeg\"" argument, etc. .

So this test is a total catastrophe.

The question then comes, is this a bug or a feature?

I can totally see that it is your intended design of gsc+gambc-cc that those arguments should be passed exactly verbatim all the way to the C compiler, it makes sense, for instance as a correctness and a security measure.

So what I am asking here is if you have any thoughts about the convenience factor, or if you have any design thought here or this just design choice just was arbitrary.

Anyhow in the absence of shell-evaluation of pkg-config anywhere else, I need to add it explicitly, meaning then that the compile-file command should be:

(compile-file "test.scm"
cc-options: (myshellrun "pkg-config --cflags \"libjpeg\"")
ld-options: (myshellrun "pkg-config --libs \"libjpeg\"")
)

where myshellrun is a procedure that involves open-process and reads its output to a string.

Please confirm that this indeed is the intended best practice for solving this problem.

Thanks!