<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126954>126954</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            lld-link library search should be case-insensitive for compatibility with MSVC artifacts
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            lld:COFF
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          rnk
      </td>
    </tr>
</table>

<pre>
    MSVC tools produce `.obj` files that refer to `MSVCRT`, `OLDNAMES`, and `LIBCMT`, but they distribute files with lower-cased names:
```
$ cl  -c t.cpp   && dumpbin -directives t.obj | grep -i defaul
Microsoft (R) C/C++ Optimizing Compiler Version 19.41.34123 for x64
Copyright (C) Microsoft Corporation. All rights reserved.

t.cpp
   /DEFAULTLIB:libcpmt
 /DEFAULTLIB:LIBCMT
   /DEFAULTLIB:OLDNAMES

$ cl -MD  -c t.cpp   && dumpbin -directives t.obj | grep -i defaul
Microsoft (R) C/C++ Optimizing Compiler Version 19.41.34123 for x64
Copyright (C) Microsoft Corporation. All rights reserved.

t.cpp
   /DEFAULTLIB:msvcprt
 /DEFAULTLIB:MSVCRT
   /DEFAULTLIB:OLDNAMES

$ ls /c/Program\ Files/Microsoft\ Visual\ Studio/2022/Professional/VC/Tools/MSVC/14.41.34120/lib/x64/
aligned_new.lib libcmt.lib msvcmrtd.lib
...
clang_rt.fuzzer_MT-x86_64.lib libconcrtd1.amd64.pdb         oldnames.lib
```

Clang and LLVM use lower-cased filenames for auto-linking:
```
$ git grep -i oldnames ../clang ../llvm
../clang/lib/Driver/ToolChains/Clang.cpp: CmdArgs.push_back("--dependent-lib=oldnames");
...
```

This presents a portability problem when cross-linking for Windows from Linux or other case-sensitive platforms. Ideally, LLD should be able to handle MSVC-produced artifacts as they are. We could make this as simple as checking for lower-cased filenames as part of our `findFile` implementation.

I was almost certain there was already an issue covering this, but github issue search isn't that great, and I hoped that as I started to file this one, it would magically point me to "similar issues", but I've made it this far and it hasn't done that yet, so I'm hitting Create...
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzkVsFu2zgQ_Rr6MrAgU7YTH3xQ5AoI4GwXTTY9BpQ4kthQpEBSdt2vXwwlO2iRw943CGCJ1AzfPL43pPBetQZxzzYPbHNYiDF01u2deV9UVl72T8-vBQRrtYfBWTnWCGybJrb6wbYpNEqjh9CJAA4bdBAsTVPQtxe2TRkv6P3r8fBX_vTleR4RRtLo8fGheLp-VY0BQocXkMoHp6ox4Jz9rEIH2p7RLWvhUYIRPXqW5SzNKXj6T3PG11BrgGUNIamHAQAY3zK-BTn2Q6UMLKVyWAd1IsxUArC7AlqHAywVSGzEqFmaP6naWW-bAIzff2N8BwXjZcH4A-MP8HUIqle_lGmhsP2gNDp4ReeVNbDaJetVkq1XPIPGOvi5XbM0L-xwcartYr6C8n2sUFg3WCeCsiaBXGuIH3pw6NGdUCZUWJrHgliax5rKw5cy_-f4cnx8YFmuVVUPfaDJP6dmgj8Nu21JzD9zt3w6_O_46_2pHtyn_M0y_o_8aU8f1YyXfzvbOtGzTQElSZjx8oaYBl-VH4Wmp-cwSmUZL3nK-RTZoCcuhGa8fCXiXsh8lOI5vq7WV45SxkutKsZL4omXLM2FJjPLN4PnRKsKSBx9iI9UZ--CpBeW5klC1NRamPbNhaQZf_1C9_b0svx5v33brm_R1tQuyFUierldJ4Os4PpntYxOnBP-ZsU0LyhzdPrx-PoEo8ffPEzWjtFxn8UY7FIr865M-7mxWxVuQrsuDElChMeF4qPWpz6Wdh2-EXRw6oRuJrPohDLEaMQYlZHlUPQyd61PhtF3b5Wo3xm_Z5wvlxIHNBJNWFKu7HBdntGO7Vj2cGPzDwpeOkVNEz2a4EHAYF0QldIqXKiXVhp7OHdogKThr_VHQr4rI-3ZQ-NsD0dlxp9gHdjQoQMicOnReEVOhEGL0FjX-wQeJQqtL9ROj8cD-M6OWkKFICqN1Jo7YaRGICUt524uQbigGlETRD-1YOEwge8IdYzvxTtCoFqEB6_6QSM91R3WN7yfb63wMAgXwDZgR0ctv1FGkiXo7IiZejRhcu_E2SOchQehe-sD1OiCUIZAOZwnHAp5AWFAeT8SxBM6QkEAr-dIq0I3VvMXHoWrO1DeMH4XprOqdSjC9SR6hM4OKKcZ4eERfBAu0IiNxUzFW4MUoQKcZ1paVRPdMFhlAvSRYca5V73Swk3LTyqZYD0yfndC6IVEShOzNsJFECpAJ2aI0hqc0FwwovQ2xvbQqRBi4yT8mCTJQu4zuct2YoH71V22y-63fL1adHvJZVNxub1fre7rtbxLKyk538hqhWsUd-lC7XnKNylf8dX9Js12SZY2WGebbH23rSVukK1T7IXSCbkqsa5dxIL2K77dbdYLLSrUPt4aONdasiwvvpYllbs5LNyeopbV2Hq2TrXywX_kCSpo3Gsto-SpyzjhLteN-lBtFLoyH1InpdW2H0RQs43i3SBeUW4qXoxO77sQhnhF4CXj5aSHpLb9tUlMP-SBH1gHxsvrZpVzeac9_zcAAP__ZVPpMQ">