How to compile the C example (using the static library)

[rchastain]

Hello!

Question of a beginner.

I am trying without success the compile this C example.

Here are the steps I followed.

First I appended the line crate-type = ["staticlib"] in Cargo.toml.

[lib]
# There are no benchmarks in the library code itself
bench = false
# Doc tests fail when some features aren't present. The easiest way to work
# around this is to disable automatic doc testing, but explicitly test them
# with `cargo test --doc`.
doctest = false
crate-type = ["staticlib"]

Then I built the library with cargo build --release.

Then I copied libregex.a in the folder where is example.c.

And I tried several commands to compile. My last attempt was this one:

LC_ALL=C gcc -o example example.c libregex.a -I./regex-230215/regex-capi/include  -L. -lregex

I get this:

[roland@localhost rure]$ sh build-c.sh
/usr/bin/ld: /tmp/ccOYlfWB.o: in function `test_is_match':
example.c:(.text+0x1a): undefined reference to `rure_compile_must'
/usr/bin/ld: example.c:(.text+0x42): undefined reference to `rure_is_match'
/usr/bin/ld: example.c:(.text+0x60): undefined reference to `rure_free'
...

I tried with the release 1.0.0 and also with the latest code from the repository.

Please could you tell me what I am doing wrong?

[BurntSushi]

It's hard to say because I don't think you've given me a full reproduction of your issue. A full repro means including all inputs and commands you're running. That is, I should be able to take the commands and inputs you give me, run them on my machine and (hopefully) get the same error as you. Then I can better help you resolve the problem. But right now, I would for example need to guess as to the contents of example.c. And also how exactly you're building the library.

Here's an example of what I would expect a reproduction to look like. In an empty directory:

$ git clone https://github.com/rust-lang/regex
$ cd regex/regex-capi
$ cargo build --release
$ cd ../..              
$ cp regex/target/release/librure.a ./libregex.a
$ cp regex/regex-capi/ctest/test.c example.c
$ LC_ALL=C gcc -o example example.c libregex.a -I./regex/regex-capi/include  -L. -lregex
$ ./example                              
PASSED: test_is_match
PASSED: test_shortest_match
PASSED: test_find
PASSED: test_captures
PASSED: test_iter
PASSED: test_iter_capture_names
PASSED: test_flags
PASSED: test_compile_error
PASSED: test_compile_error_size_limit
PASSED: test_regex_set_match
PASSED: test_regex_set_options
PASSED: test_regex_set_match_start
PASSED: test_escape

I'll also note that your gcc command looks a little more complicated than what is necessary. For example, gcc -o example example.c -I./regex/regex-capi/include -L. -lregex also works for me.

[rchastain]

Thank you for your answer.

I don't know why, your method doesn't work here (Linux Mageia 64-bit, GCC 10.4.0).

[roland@localhost test]$ git clone https://github.com/rust-lang/regex
Clonage dans 'regex'...
remote: Enumerating objects: 16822, done.
remote: Counting objects: 100% (1253/1253), done.
remote: Compressing objects: 100% (429/429), done.
remote: Total 16822 (delta 852), reused 1126 (delta 802), pack-reused 15569
Réception d'objets: 100% (16822/16822), 13.87 Mio | 3.24 Mio/s, fait.
Résolution des deltas: 100% (10937/10937), fait.
[roland@localhost test]$ cd regex/regex-capi
[roland@localhost regex-capi (master)]$ cargo build --release
    Updating crates.io index
  Downloaded libc v0.2.139
  Downloaded 1 crate (639.0 KB) in 1.41s
   Compiling memchr v2.5.0
   Compiling libc v0.2.139
   Compiling regex-syntax v0.6.28 (/home/roland/Documents/basic/rure/test/regex/regex-syntax)
   Compiling aho-corasick v0.7.20
   Compiling regex v1.7.1 (/home/roland/Documents/basic/rure/test/regex)
   Compiling rure v0.2.2 (/home/roland/Documents/basic/rure/test/regex/regex-capi)
    Finished release [optimized + debuginfo] target(s) in 55.07s
[roland@localhost regex-capi (master)]$ cd ../.. 
[roland@localhost test]$ cp regex/target/release/librure.a ./libregex.a
[roland@localhost test]$ cp regex/regex-capi/ctest/test.c example.c
[roland@localhost test]$ LC_ALL=C gcc -o example example.c libregex.a -I./regex/regex-capi/include  -L. -lregex
/usr/bin/ld: libregex.a(std-05737cf45bd30456.std.428b0c25-cgu.0.rcgu.o): in function `std::sys::unix::thread::guard::get_stack_start':
/rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/sys/unix/thread.rs:720: undefined reference to `pthread_attr_getstack'
/usr/bin/ld: libregex.a(std-05737cf45bd30456.std.428b0c25-cgu.0.rcgu.o): in function `std::sys::unix::thread_local_key::get':
/rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/sys/unix/thread_local_key.rs:22: undefined reference to `pthread_getspecific'
/usr/bin/ld: libregex.a(std-05737cf45bd30456.std.428b0c25-cgu.0.rcgu.o): in function `std::sys::unix::thread_local_key::set':
/rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/sys/unix/thread_local_key.rs:16: undefined reference to `pthread_setspecific'
/usr/bin/ld: libregex.a(std-05737cf45bd30456.std.428b0c25-cgu.0.rcgu.o): in function `std::sys::unix::thread_local_key::create':
/rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/sys/unix/thread_local_key.rs:10: undefined reference to `pthread_key_create'
...
collect2: error: ld returned 1 exit status

[rchastain]

OK, I think I found the right command.

[roland@localhost test]$ LC_ALL=C gcc -o example example.c -I./regex/regex-capi/include -L. -lregex -lpthread -ldl
[roland@localhost test]$ ./example
PASSED: test_is_match
PASSED: test_shortest_match
PASSED: test_find
PASSED: test_captures
PASSED: test_iter
PASSED: test_iter_capture_names
PASSED: test_flags
PASSED: test_compile_error
PASSED: test_compile_error_size_limit
PASSED: test_regex_set_match
PASSED: test_regex_set_options
PASSED: test_regex_set_match_start
PASSED: test_escape
[roland@localhost test]$ 

Problem solved, thank you.

[BurntSushi]

Interesting. It looks like I called this out somewhat in the compile script:

regex/regex-capi/ctest/compile

Line 8 in a9b2e02

# -lutil -ldl -lpthread -lgcc_s -lc -lm -lrt -lutil -lrure

But I don't know why my gcc command above worked without linking pthread (and others). Glad it's working for you now though!