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.

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 · 2025-09-17T08:41:50Z

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

SicongLiu2000 · 2025-10-09T17:11:31Z

language-extensions/dotnet-core-CSharp/build/linux/build-dotnet-core-CSharp-extension.ps1

@@ -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?

language-extensions/dotnet-core-CSharp/build/linux/build-dotnet-core-CSharp-extension.ps1

language-extensions/dotnet-core-CSharp/build/linux/create-dotnet-core-CSharp-extension-zip.ps1

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

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

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

+#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

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

+    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

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

 #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

SicongLiu2000 · 2026-02-12T21:48:54Z

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

 #include <hostfxr.h>
+#include <nethost.h>

+#if defined(_WIN32) || defined(WINDOWS)


Nit: STR/CH macros are already defined identically in DotnetEnvironment.h (lines 18-23). Defining them in both the header and the .cpp is redundant and creates maintenance drift risk. Consider removing the duplicate here and relying on the header definitions.

SicongLiu2000 · 2026-02-12T21:48:54Z

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

 #include <hostfxr.h>

+#if defined(_WIN32) || defined(WINDOWS)
 #define STR(s) L ## s


The two adjacent #ifdef blocks for the same condition could be merged. Consider defining PATH_SEPARATOR alongside STR/CH in the block above rather than in a separate block.

SicongLiu2000 · 2026-02-12T21:48:54Z

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

+2. Run [create-dotnet-core-CSharp-extension-zip.ps1](./build/windows/create-dotnet-core-CSharp-extension-zip.cmd) which will generate: \
+        - PATH/TO/ENLISTMENT/build-output/dotnet-core-CSharp-extension/linux/release/packages/dotnet-core-CSharp-lang-extension.tar.gz
+        This tarball can be used in CREATE EXTERNAL LANGUAGE, as detailed in the tutorial in the Usage section below.



The link text says .cmd but the actual file is a .ps1 script, and the path points to ./build/windows/ rather than ./build/linux/. Should be:
[build-dotnet-core-CSharp-extension.ps1](./build/linux/build-dotnet-core-CSharp-extension.ps1)

MarkpageBxl added 9 commits September 17, 2025 09:54

Make Logger and nativecsharpextension compile on Linux.

72625a9

Make DotnetEnvironment compile on Linux.

d52769f

Add build script for Linux.

02420c2

Add archive script for Linux.

1b8b12e

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

Bump .NET from unsupported 6.0 to 8.0.

e53d68b

Use nethost to lookup hostfxr on Linux.

97535d3

Add debug compiler flag when building in debug.

db1ec51

Fix Linux/Windows portability issues.

493a29b

MarkpageBxl mentioned this pull request Sep 17, 2025

Add Linux support for .NET #63

Open

Add documentation about C# on Linux.

fa06738

SicongLiu2000 reviewed Oct 9, 2025

View reviewed changes

MarkpageBxl added 2 commits October 10, 2025 10:31

Fix _WIN32 preprocessor symbol typo.

ba5507d

Cleanup argument loop in Linux scripts.

04be02e

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

View reviewed changes

SicongLiu2000 reviewed Feb 12, 2026

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MarkpageBxl commented Sep 17, 2025

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Pull Request Overview

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SicongLiu2000 commented Nov 13, 2025

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

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