Add Linux support to .NET language extension by MarkpageBxl · Pull Request #64 · microsoft/sql-server-language-extensions

MarkpageBxl · 2025-09-17T08:39:49Z

This PR adds Linux support to the .NET language extension, which currently only supports Windows.

This involves the following:

Creating scripts for building and shipping the Linux native library. PowerShell was chosen as a scripting language to serve as a potential base for a cross-platform script.
The Windows-specific APIs used in the native library have been augmented with Linux library calls, guarded by standard preprocessor defines.
Due to differences in the .NET runtime lookup logic in hostfxr between Linux and Windows, using a hardcoded hostfxr library path was a no go for portability (e.g. .NET packages on RHEL and Debian do not install .NET in the same base directories). Instead, we make use of nethost (in the form of the libnethost.a static library provided by the .NET runtime) to first do the hostfxr lookup. This approach has the advantage of honoring DOTNET_ROOT and install_location files if they exist, which hostfxr does not.

Additionally, this bumps references to net6.0 up to net8.0, since the former is EOL.

At this point, this has been tested manually on SQL Server running on Ubuntu 22.04 LTS. A .NET 8.0 assembly was successfully executed.

MarkpageBxl · 2025-09-17T08:41:50Z

@microsoft-github-policy-service agree company="Raincode srl"

SicongLiu2000 · 2025-10-09T17:11:31Z

@@ -0,0 +1,106 @@
+#!/usr/bin/env pwsh


Why are we using powershell script for linux instead of bash script?

As written in the description, PowerShell was chosen as a scripting language to serve as a potential base for a cross-platform script. If this is not desired, I can rewrite it in bash.

Do you mean this script can be used for both windows/linux now or we should have a follow-up work item for this?

If PowerShell is acceptable, then it would indeed probably make sense to harmonize this on Windows and Linux. I would suggest creating a distinct separate work item for this.

Copilot

Pull Request Overview

This PR adds Linux support to the .NET language extension, which previously only supported Windows. The changes include:

Platform-specific conditional compilation using preprocessor defines to support both Windows and Linux
Integration of nethost library for dynamic hostfxr lookup on Linux (avoiding hardcoded paths)
Updated build artifacts and project files to target .NET 8.0 (from .NET 6.0, which is EOL)
Platform-specific APIs for file operations, dynamic library loading, and path handling

Reviewed Changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
Microsoft.SqlServer.CSharpExtensionTest.csproj	Updated target framework from net6.0 to net8.0
Microsoft.SqlServer.CSharpExtension.csproj	Updated target framework from net6.0 to net8.0
RegexSample.csproj	Updated target framework from net6.0 to net8.0
Logger.cpp	Removed Windows-specific includes (stdio.h, windows.h)
Logger.h	Removed stdio.h include
DotnetEnvironment.cpp	Added platform-specific code for library loading, path handling, and hostfxr lookup using nethost
DotnetEnvironment.h	Added platform-specific macros and definitions for path separators and string types
nativecsharpextension.h	Guarded windows.h include with platform check
nethost.h	Added header file for nethost API
libnethost.a	Added static library for nethost (Linux)

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Copilot · 2025-11-10T22:46:13Z

+#if defined(_WIN32) || defined(WINDOWS)
+    m_root_path(to_utf16_str(language_path))
+#else
+    m_root_path(language_path)
+#endif


[nitpick] The conditional initialization of m_root_path in the constructor initializer list could be simplified. Consider using a helper function to convert the path conditionally, which would make the code cleaner and easier to maintain. For example, create a convert_path(const std::string& path) function that returns either the UTF-16 or UTF-8 version based on the platform.

Copilot · 2025-11-10T22:46:13Z

+    char buffer[4096];
+    size_t buffer_size = sizeof(buffer);
+    if (get_hostfxr_path(buffer, &buffer_size, nullptr) != 0) {
+        return false;
+    }


[nitpick] The hardcoded buffer size of 4096 bytes should be defined as a named constant (e.g., constexpr size_t HOSTFXR_PATH_BUFFER_SIZE = 4096;) to improve code maintainability and make it easier to adjust if needed.

Copilot · 2025-11-10T22:46:13Z

 #include "DotnetEnvironment.h"
 #include "Logger.h"
+
+#if defined(_WIN32) || defined(WINDOWS)


[nitpick] The platform check uses both _WIN32 and WINDOWS macros. The _WIN32 macro is the standard Microsoft compiler define for Windows (both 32-bit and 64-bit). The WINDOWS macro appears to be custom. Consider using only _WIN32 for consistency with common practice, or document why both are needed if there's a specific reason.

SicongLiu2000 · 2025-11-13T01:50:23Z

@MarkpageBxl , have you ever met this error:

Error: Could not find a part of the path
'/home/mssql_satellite/externallibrariessandboxprivatepath'

SicongLiu2000

Code Review — PR #64: Add Linux support to .NET language extension

I tested this end-to-end in a Docker container (SQL Server 2022 + mssql-server-extensibility on Ubuntu) and confirmed the Linux path works — the regex sample returns correct results via sp_execute_external_script.

Overall this is a clean PR. The platform #ifdef guards, nethost integration for hostfxr discovery, and the Linux build scripts are well done. A few comments below.

Issues

1. STR/CH macros duplicated in both .h and .cpp
DotnetEnvironment.h and DotnetEnvironment.cpp both define STR(s) and CH(c) with the same #ifdef guards. They should be defined in only one place (the header) to avoid maintenance drift.

2. README link mismatch in Linux build section
The Linux build instructions reference build-dotnet-core-CSharp-extension.ps1 but the link text shows .cmd. Same for the archive script.

3. Pre-existing issues on main (not from this PR, but worth noting)
While testing, I found critical memory safety bugs in CSharpParamContainer.cs that already exist on main:

ReplaceNumericParam<T>: uses &value (dangling stack pointer) instead of the correct GCHandle.Alloc(array, Pinned) + AddrOfPinnedObject() pattern. This corrupts all numeric output parameters.
ReplaceStringParam: fixed block pointer escapes its scope while the GCHandle is not pinned. This corrupts string output parameters.
GetStrLenNullMap/ReplaceParam for DotNetChar: uses .Length (char count) instead of Encoding.UTF8.GetByteCount() — wrong for multi-byte UTF-8.

These should be tracked as a separate issue/fix.

Positive

nethost/get_hostfxr_path() for Linux hostfxr discovery is the right approach
PATH_SEPARATOR macro is clean
Build scripts (.ps1) are well-structured with proper error handling
net8.0 target upgrade is appropriate (net6.0 is EOL)
End-to-end verified working on Linux

SQL Server on Linux expects a .tar.gz file instead of a .zip when using CREATE EXTERNAL LANGUAGE.

We will use the nethost to locate the system's installed hostfxr, as using a local libhostfxr.so breaks the .NET runtime lookup. nethost contains the logic needed to find the .NET root based on the DOTNET_ROOT environment variable or the install_location configuration file, which we will require for .NET runtime lookup on diverging Linux distributions (e.g. RHEL and Debian packages not installing .NET in the same base directories).

MarkpageBxl · 2026-03-27T08:03:08Z

I have rebased on main, and made an additional fallout fix re the use of the DOTNET_ROOT environment variable in DotnetEnvironment.cpp, as the existing code was Windows only.

MarkpageBxl · 2026-03-27T08:20:44Z

I also assume we should probably upgrade to net10.0 at this point, though that could be a separate work item as well.

- Replace PowerShell build scripts with bash (build, archive, restore) - Remove checked-in libnethost.a; fetch at build time via restore-packages.sh - Add libnethost.a existence guard in build script - Use vswhere.exe for VS detection in Windows build scripts - Add convert_string() abstraction in DotnetEnvironment - Conditional nethost.h include (Linux only), HOSTFXR_PATH_BUFFER_SIZE constant - Add LOG_ERROR on hostfxr lookup failure - Fix load_hostfxr comment (was incorrectly named get_export) - Add Linux test build/run scripts and CMake platform support - Add -fshort-wchar and fix wstring ABI issues in test code - Add platform-conditional HintPath in test csproj - Add Linux dlopen/dlsym equivalents in test API code - Add Dockerfile for Linux build/test CI

MarkpageBxl mentioned this pull request Sep 17, 2025

Add Linux support for .NET #63

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SicongLiu2000 reviewed Oct 9, 2025

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SicongLiu2000 requested a review from Copilot November 10, 2025 22:44

Copilot started reviewing on behalf of SicongLiu2000 November 10, 2025 22:44 View session

Copilot finished reviewing on behalf of SicongLiu2000 November 10, 2025 22:45

Copilot AI reviewed Nov 10, 2025

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SicongLiu2000 reviewed Feb 12, 2026

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Comment thread language-extensions/dotnet-core-CSharp/src/native/DotnetEnvironment.cpp Outdated

Comment thread language-extensions/dotnet-core-CSharp/include/DotnetEnvironment.h

Comment thread language-extensions/dotnet-core-CSharp/README.md

MarkpageBxl added 11 commits March 20, 2026 15:13

Make Logger and nativecsharpextension compile on Linux.

1dbb48f

Make DotnetEnvironment compile on Linux.

704e592

Add build script for Linux.

2dd039b

Add archive script for Linux.

222d4f3

SQL Server on Linux expects a .tar.gz file instead of a .zip when using CREATE EXTERNAL LANGUAGE.

Use nethost to lookup hostfxr on Linux.

774d4dc

Add debug compiler flag when building in debug.

d4afec8

Fix Linux/Windows portability issues.

f7456f2

Add documentation about C# on Linux.

8ab5025

Fix _WIN32 preprocessor symbol typo.

7a99b8a

Cleanup argument loop in Linux scripts.

86d15ea

MarkpageBxl force-pushed the dotnet-linux branch from 04be02e to 86d15ea Compare March 20, 2026 14:15

MarkpageBxl added 3 commits March 27, 2026 08:44

Fix doc links.

dd2f532

Rationalize defines.

ca1d83a

Handle DOTNET_ROOT DotnetEnvironment on Linux.

c47d3f3

MarkpageBxl requested a review from SicongLiu2000 March 30, 2026 07:06

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Pull Request Overview

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Code Review — PR #64: Add Linux support to .NET language extension

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MarkpageBxl commented Mar 27, 2026

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