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[rustbuild] cannot link to printf with MSVC on AppVeyor #42830
Description
Spun off from #42777 (comment). The test case for error code E0060 contains an invocation to the C function printf. On MSVC, performing doctest on this test case failed with
= note: rust_out.0.o : error LNK2019: unresolved external symbol printf referenced in function _ZN8rust_out4main17ha22022d8940e3e88E
Currently I'm checking if there is any missing linker args should be added to make the pass without #[cfg]ing it out.
Minimal test case
Code (copy of E0060), see https://github.com/kennytm/test-term-coloring/tree/43a23596b
/**
```
# use std::os::raw::{c_char, c_int};
# extern "C" { fn printf(_: *const c_char, ...) -> c_int; }
unsafe {
use std::ffi::CString;
let fmt = CString::new("test\n").unwrap();
printf(fmt.as_ptr());
let fmt = CString::new("number = %d\n").unwrap();
printf(fmt.as_ptr(), 3);
let fmt = CString::new("%d, %d\n").unwrap();
printf(fmt.as_ptr(), 10, 5);
}
```
*/
pub fn wut() {}Test result, see https://ci.appveyor.com/project/kennytm/test-term-coloring/build/1.0.2
Doc-tests test-term-coloring
running 1 test
error: linking with `link.exe` failed: exit code: 1120
|
= note: "C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\bin\\amd64\\link.exe" "/NOLOGO" "/NXCOMPAT" "/LIBPATH:C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "C:\\Users\\appveyor\\AppData\\Local\\Temp\\1\\rustdoctest.xIdH18C27InS\\rust_out.0.o" "/OUT:C:\\Users\\appveyor\\AppData\\Local\\Temp\\1\\rustdoctest.xIdH18C27InS\\rust_out.exe" "/OPT:REF,NOICF" "/DEBUG" "/LIBPATH:C:\\projects\\test-term-coloring\\target\\x86_64-pc-windows-msvc\\debug\\deps" "/LIBPATH:C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "/LIBPATH:C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "std-7c926edf41e020d3.dll.lib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libcompiler_builtins-ce3e1312c7c980ee.rlib" "advapi32.lib" "ws2_32.lib" "userenv.lib" "shell32.lib" "msvcrt.lib"
= note: rust_out.0.o : error LNK2019: unresolved external symbol printf referenced in function _ZN8rust_out4main17ha22022d8940e3e88E
C:\Users\appveyor\AppData\Local\Temp\1\rustdoctest.xIdH18C27InS\rust_out.exe : fatal error LNK1120: 1 unresolved externals
error: aborting due to previous error(s)
thread 'rustc' panicked at 'Box<Any>', src\librustc_errors\lib.rs:512
note: Run with `RUST_BACKTRACE=1` for a backtrace.
thread 'rustc' panicked at 'couldn't compile the test', src\librustdoc\test.rs:278
test src\lib.rs - wut (line 1) ... FAILED
failures:
failures:
src\lib.rs - wut (line 1)
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
Activity
retep998 commentedon Jun 22, 2017
With the new Universal CRT, msvc has switched to all the printf functions being inline wrapper functions. This is a known issue that has been hit before in Rust If you really want
printfthe solution is to link againstlegacy_stdio_definitions.libwhich provides the printf wrapper functions as normal symbols to link against, but only when using a newer msvc that uses the Universal CRT. For older versions (such as VS 2013) that library does not exist and you can useprintfnormally.kennytm commentedon Jun 22, 2017
Looks like adding
#[cfg_attr(all(windows, target_env="msvc"), link(name="legacy_stdio_definitions", kind="static"))]to the
externblock works.It is not possible to
cfgthe linker version in the doctest. As we are just using the default VS version on AppVeyor i.e. VS2015, I'll just add the attribute and ignore VS2013.retep998 commentedon Jun 22, 2017
Please don't use
kind="static". Either usedyliborstatic-nobundle.staticshould only be used when the bundling behavior is necessary.kennytm commentedon Jun 22, 2017
@retep998 Thanks.
static-nobundleshould be the only option then?legacy_stdio_definitionsdoes not seem to be a dynamic library.