Include all dlerror messages to DllNotFoundException

[HJLeee]

#70963

[jkotas]

I expect that there are many situations where the dlerror error message is actually helpful. Those cases will be less diagnosable after this change.

If there are situations where the error message returned by dlerror is misleading, would it be more appropriate to fix that in libdl?

[HJLeee]

Narrow down the impact by eliminating overridden error string.

The root cause of incorrect error message is LoadNativeLibraryBySearch tries its best for loading p/invoke library.
For a given p/invoke library name libpinvoke.so, it attempts 4 times with below name combinations to load the library.

currLibNameVariation = {<SBuffer> = {m_size = 34, m_allocation = 82, m_flags = 12, {m_buffer = 0x5583e6df10 "l", m_asStr = 0x5583e6df10 u"libpinvoke.so.so"}},
  static MINIMUM_GUESS = 20, static s_EmptyBuffer = "\000", static s_ACP = 65001, static s_Empty = 0x7fad806290 <s_EmptySpace>}

currLibNameVariation = {<SBuffer> = {m_size = 40, m_allocation = 82, m_flags = 12, {m_buffer = 0x5583e6df10 "l", m_asStr = 0x5583e6df10 u"liblibpinvoke.so.so"}},
  static MINIMUM_GUESS = 20, static s_EmptyBuffer = "\000", static s_ACP = 65001, static s_Empty = 0x7fad806290 <s_EmptySpace>}

currLibNameVariation = {<SBuffer> = {m_size = 28, m_allocation = 82, m_flags = 12, {m_buffer = 0x5583e6df10 "l", m_asStr = 0x5583e6df10 u"libpinvoke.so"}}, static MINIMUM_GUESS = 20,
  static s_EmptyBuffer = "\000", static s_ACP = 65001, static s_Empty = 0x7fad806290 <s_EmptySpace>}

currLibNameVariation = {<SBuffer> = {m_size = 34, m_allocation = 82, m_flags = 12, {m_buffer = 0x5583e6df10 "l", m_asStr = 0x5583e6df10 u"liblibpinvoke.so"}},
  static MINIMUM_GUESS = 20, static s_EmptyBuffer = "\000", static s_ACP = 65001, static s_Empty = 0x7fad806290 <s_EmptySpace>}

In this scenario, the last error message for dlopen() attempts is kept and it is not possible to determine what error message is beneficial to the developer.
With update, I think error message from dlerror() will be printed when it is not overwritten.

Another possible patch would be keeping error message for exact libname only.

[jkotas]

If I am reading the code correctly, this will pretty much always erase the dlerror message. There is pretty much always more than one attempt to load library. The first attempt will set the error message, the second attempt will erase it, and so the error message will be lost.

[jkotas]

Since we cannot tell which error message is the best one, should keep all error messages (eliminate the duplicates) and include all of them in the exception?

[HJLeee]

System.DllNotFoundException: Unable to load shared library 'libpinvoke.so' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: libpinvoke.so.so: cannot open shared object file: No such file or directory liblibpinvoke.so.so: cannot open shared object file: No such file or directory /opt/share/libpinvoke.so: wrong ELF class: ELFCLASS32 libpinvoke.so: cannot open shared object file: No such file or directory liblibpinvoke.so: cannot open shared object file: No such file or directory

[jkotas]

Could you please make the same change in the managed version at

runtime/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeLibrary.NativeAot.Unix.cs

Line 54 in e297470

_errorMessage = message;

?

[HJLeee]

I'd love to make a patch for NativeAot.
Currently, I'm having a trouble with setting up NativeAot test env like below.

dlerror.csproj : error NU1102: Unable to find package Microsoft.NETCore.App.Runtime.linux-x64 with version (= 7.0.0-preview.5.22301.12)
dlerror.csproj : error NU1102:   - Found 1 version(s) in local [ Nearest version: 7.0.0-dev ]
dlerror.csproj : error NU1101: Unable to find package Microsoft.AspNetCore.App.Runtime.linux-x64. No packages exist with this id in source(s): local

This is my nuget.config.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <!--To inherit the global NuGet package sources remove the <clear/> line below -->
    <clear />
    <add key="local" value="${runtime}/artifacts/packages/Release/Shipping" />
    <!--add key="nuget" value="https://api.nuget.org/v3/index.json" /-->
  </packageSources>
</configuration>

Please help me setting up the test env.

[HJLeee]

NativeAot message is checked by editing nativeaot smoke test.

      nativeaot/SmokeTests/PInvoke/PInvoke/PInvoke.sh [FAIL]
        Unhandled Exception: System.DllNotFoundException: Unable to load shared library 'PInvokeNative' or one of its dependencies. In order to help diagnose loading problems, consider using a tool like strace. If you're using glibc, consider setting the LD_DEBUG environment variable:
        PInvokeNative.so: cannot open shared object file: No such file or directory
        libPInvokeNative.so: wrong ELF class: ELFCLASS32
        PInvokeNative: cannot open shared object file: No such file or directory
        libPInvokeNative: cannot open shared object file: No such file or directory

           at System.Runtime.InteropServices.NativeLibrary.LoadLibErrorTracker.Throw(String) + 0x4e
           at Internal.Runtime.CompilerHelpers.InteropHelpers.FixupModuleCell(InteropHelpers.ModuleFixupCell*) + 0x103
           at Internal.Runtime.CompilerHelpers.InteropHelpers.ResolvePInvokeSlow(InteropHelpers.MethodFixupCell*) + 0x35
           at PInvokeTests.Program.Square(Int32) + 0x21
           at PInvokeTests.Program.TestBlittableType() + 0x1a
           at PInvokeTests.Program.Main(String[]) + 0x9
           at PInvoke!<BaseAddress>+0x2ac21b

[jkotas]

LGTM.

@dotnet/interop-contrib Do you have any feedback?

[AaronRobinsonMSFT]

@dotnet/interop-contrib Do you have any feedback?

Nope. Seems reasonable to me. @HJLeee Thank you.

[HJLeee]

It's my pleasure and happy to participate in dotnet runtime.