link error undefined reference

[toplinuxsir]

I link c++ libray (libmylib.so ) , with g++ -lmylib , It works ok, and link success,
But with rust ,I have pass the -lmylib, compiles ok, and always link error:
'
/usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x106): undefined reference to USB5622E_GetNetCfgA' /usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x351): undefined reference to USB5622E_AI_GetRateInfo'
/usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x4d0): undefined reference to USB5622E_AI_VerifyParam' /usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x4f7): undefined reference to USB5622E_AI_InitTask'
/usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x508): undefined reference to USB5622E_AI_StartTask' /usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x581): undefined reference to USB5622E_AI_SendSoftTrig'
/usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x5a0): undefined reference to USB5622E_AI_ReadBinary' /usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x875): undefined reference to USB5622E_DEV_Release'
/usr/bin/ld: callc.d2qs7r1b-cgu.0:(.text._ZN5callc4main17h70fed83690e9e7b8E+0x961): undefined reference
'

[emilio]

Bindgen doesn't take care of linking anything. Are you passing the right flags to rustc? Like println!("cargo:rustc-link-lib=mylib") from build.rs or such?

[toplinuxsir]

@emilio
Yes, I have pass the right flags to rustc
my build.rs

fn main() {
    println!(r"cargo:rustc-link-search=/usr/lib/mylib");


    println!("cargo:rustc-link-lib=static=stdc++");
    println!(r"cargo:rustc-link-lib=mylib");
}

[nagisa]

I started hitting something similar recently. More often than not it is because rustc reorders the -l flags before their use because it is missing the dependency information due to missing #[link(name="...")].

[toplinuxsir]

@nagisa How to resolve it ? Thanks

[emilio]

I think this is not a bindgen issue itself given the above... But a minimal repro would go a long way. Please reopen if this turns out to be an issue that should be fixed in bindgen.

[nagisa]

@emilio bindgen currently does not provide the means to add #[link(name="...")] attributes to extern blocks it generates. Something like this reproducer from rust-lang/rust#65610 should be trivially adaptable to use bindgen.

[mrozekma]

I'm a bindgen novice, but am confused why this isn't a bigger problem for users. I have to edit the generated bindings to add #[link(...)] attributes on the functions or the final link will fail when I try to call them, but the documentation seems to expect I'll just be able to use the generated bindings as-is.

[mengwanguc]

I totally agree with @mrozekma , and I do think it's a big problem for me as I need to add #[link(name="...")] manually for every function I'm calling in the generated "binding.rs". bindgen should be able to do it for users