Test sccache with temp copy by agocke · Pull Request #124074 · dotnet/runtime

agocke · 2026-02-06T08:02:36Z

No description provided.

Copilot

Pull request overview

This PR adds experimental sccache (compiler caching tool) support for linux-x64 builds in the dotnet/runtime repository. The implementation checks for a sccache binary in the repository root and enables it for CoreCLR native builds by setting appropriate environment variables including Azure blob storage configuration.

Changes:

Adds sccache enablement logic in eng/build.sh for linux-x64 builds
Configures Azure blob storage as the cache backend (container: runtime-cache)
Sets environment variables consumed by src/coreclr/build-runtime.sh to use sccache as a CMake compiler launcher

Copilot · 2026-02-06T08:09:13Z

eng/build.sh


+# Enable sccache for linux-x64 builds if the binary is present in the repo root.
+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"


Prepending the repo root to PATH creates a security risk where any executable in the repo root can shadow system binaries during the build. Since sccache is checked to exist at a specific location, consider using the absolute path to invoke sccache instead. For example, you could set SCCACHE_PATH environment variable with the full path, and have the build scripts use that, or modify src/coreclr/build-runtime.sh to check for the sccache binary path directly rather than relying on PATH lookup.

Suggested change

export PATH="$scriptroot/..:$PATH"

export SCCACHE_PATH="$scriptroot/../sccache"

export PATH="$PATH:$scriptroot/.."

eng/build.sh

Copilot · 2026-02-06T08:09:14Z

eng/build.sh

+# Enable sccache for linux-x64 builds if the binary is present in the repo root.
+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"
+    export USE_SCCACHE=true
+    export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache
+    # SCCACHE_AZURE_CONNECTION_STRING must be set as a CI secret/environment variable.
+    echo "sccache enabled for linux-x64 build"
+fi


The sccache integration only affects CoreCLR builds because only src/coreclr/build-runtime.sh checks the USE_SCCACHE environment variable. Other native components (Mono, native libs, host/corehost) do not currently respect this setting and will not use sccache even when enabled. Consider documenting this limitation in the comment, or adding USE_SCCACHE support to other native build scripts if caching is desired for those components as well.

Copilot · 2026-02-06T08:09:14Z

eng/build.sh

+# Enable sccache for linux-x64 builds if the binary is present in the repo root.
+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"


A 15.71 MB sccache binary appears to be checked into the repository root. Since the PR title mentions "temp copy", this seems intended as a temporary test. However, checking large binaries into git history can bloat the repository permanently. Consider using a different approach for testing, such as downloading sccache in CI, or documenting that this binary should not be committed and adding it to .gitignore.

Suggested change

# Enable sccache for linux-x64 builds if the binary is present in the repo root.

if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then

export PATH="$scriptroot/..:$PATH"

# Enable sccache for linux-x64 builds if it is available on PATH.

if [[ "$os" == "linux" && "$arch" == "x64" ]] && command -v sccache >/dev/null 2>&1; then

Copilot

Pull request overview

Copilot reviewed 1 out of 2 changed files in this pull request and generated no new comments.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 1 out of 2 changed files in this pull request and generated 2 comments.

Copilot · 2026-02-06T23:21:20Z

eng/build.sh

+    fi
+    sccache -s


Because the script runs with set -e, invoking sccache -s unconditionally inside this block can abort the entire build if sccache is not on PATH (it’s only added in the connection-string branch) or if the repo-root sccache file isn’t executable. Consider either (1) calling it via the absolute path and only after verifying it’s executable, or (2) guarding the stats call behind the same enablement check / making it non-fatal.

Suggested change

fi

sccache -s

if [[ -x "$scriptroot/../sccache" ]]; then

"$scriptroot/../sccache" -s || echo "Warning: failed to collect sccache stats"

else

echo "Warning: sccache binary at '$scriptroot/../sccache' is not executable; skipping sccache stats"

fi

fi

Copilot · 2026-02-06T23:21:20Z

eng/build.sh

+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    if [[ -z "${SCCACHE_AZURE_CONNECTION_STRING:-}" ]]; then
+        echo "Warning: SCCACHE_AZURE_CONNECTION_STRING not set; sccache will not be enabled for linux-x64 build"
+    else
+        export PATH="$scriptroot/..:$PATH"
+        export USE_SCCACHE=true
+        export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache
+        # SCCACHE_AZURE_CONNECTION_STRING must be set as a CI secret/environment variable.
+        echo "sccache enabled for linux-x64 build"
+    fi
+    sccache -s


The condition only checks -f "$scriptroot/../sccache", but the code later executes sccache as a command name. If the file exists but isn’t executable (or isn’t found via PATH), this will fail. Prefer checking -x and executing "$scriptroot/../sccache" (or ensuring PATH is updated before any invocation).

Copilot

Pull request overview

Copilot reviewed 1 out of 2 changed files in this pull request and generated 2 comments.

Copilot · 2026-02-07T00:34:40Z

eng/build.sh

+    export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"
+    export SCCACHE_AZURE_NO_CREDENTIALS=true
+    echo "sccache enabled for linux-x64 build"
+    sccache -s


Because eng/build.sh runs with set -e, a failure from sccache -s (e.g., server startup failure, unsupported backend, transient network issue) will abort the entire build even though this is just a diagnostic step. Consider making the stats call best-effort (or gating it behind an explicit opt-in) so cache issues don't fail the build.

Suggested change

sccache -s

sccache -s || echo "sccache stats are unavailable; continuing without cache stats"

Copilot · 2026-02-07T00:34:40Z

eng/build.sh

+# Enable sccache for linux-x64 builds if the binary is present in the repo root.
+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"
+    export USE_SCCACHE=true
+    export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache
+    export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"
+    export SCCACHE_AZURE_NO_CREDENTIALS=true
+    echo "sccache enabled for linux-x64 build"
+    sccache -s


The guard only checks -f "$scriptroot/../sccache", but with set -e the build will still fail later if that file isn't executable or can't be invoked. It should check that the binary is executable (and ideally invoke it via its full path) before enabling USE_SCCACHE/modifying PATH.

Suggested change

# Enable sccache for linux-x64 builds if the binary is present in the repo root.

if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then

export PATH="$scriptroot/..:$PATH"

export USE_SCCACHE=true

export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache

export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"

export SCCACHE_AZURE_NO_CREDENTIALS=true

echo "sccache enabled for linux-x64 build"

sccache -s

# Enable sccache for linux-x64 builds if the binary is present and executable in the repo root.

if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" && -x "$scriptroot/../sccache" ]]; then

export PATH="$scriptroot/..:$PATH"

export USE_SCCACHE=true

export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache

export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"

export SCCACHE_AZURE_NO_CREDENTIALS=true

echo "sccache enabled for linux-x64 build"

"$scriptroot/../sccache" -s

Copilot

Pull request overview

Copilot reviewed 1 out of 2 changed files in this pull request and generated 3 comments.

Copilot · 2026-02-07T02:50:07Z

eng/build.sh

+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"


The enablement check uses -f "$scriptroot/../sccache", but that doesn't guarantee the file is executable. If the file exists without execute permissions, the later sccache -s/compiler launcher will fail and stop the build. Prefer checking -x (and/or verifying command -v sccache after updating PATH) before enabling.

Copilot · 2026-02-07T02:50:08Z

eng/build.sh


+# Enable sccache for linux-x64 builds if the binary is present in the repo root.
+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"


Prepending the repo root to PATH can unintentionally shadow system tools if a same-named executable exists in the repo (now or in the future), making builds harder to reason about. A safer pattern is to invoke sccache via an explicit absolute path and/or add only a dedicated tools directory to PATH.

Suggested change

export PATH="$scriptroot/..:$PATH"

export PATH="$PATH:$scriptroot/.."

Copilot · 2026-02-07T02:50:08Z

eng/build.sh

+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    sccache -s
+fi


The same linux/x64 + sccache-present condition is duplicated here and above. Consider factoring it into a single helper/variable to avoid future drift (e.g., if the condition or path changes in one place but not the other).

dotnet-policy-service · 2026-02-07T06:43:07Z

Tagging subscribers to this area: @dotnet/runtime-infrastructure
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.

Copilot · 2026-02-07T09:00:35Z

eng/pipelines/runtime.yml

          jobTemplate: /eng/pipelines/common/global-build-job.yml
          buildConfig: ${{ variables.debugOnPrReleaseOnRolling }}
          platforms:
          - linux_x64
-          - linux_musl_x64
-          - osx_arm64
-          - windows_x64
          jobParameters:


This change removes almost the entire job matrix from the default runtime pipeline and leaves only a single linux_x64 CoreCLR+libs build. That’s a major reduction in CI coverage and also drops the previous EvaluatePaths-based conditions (so the remaining job will run unconditionally). If the intent is to test sccache, consider adding a dedicated, explicitly-scoped job/flag instead of deleting existing legs.

Copilot · 2026-02-07T09:00:35Z

eng/build.sh

+if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
+    export PATH="$scriptroot/..:$PATH"
+    export USE_SCCACHE=true
+    export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache
+    export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"
+    export SCCACHE_AZURE_NO_CREDENTIALS=true
+    mkdir -p "$scriptroot/../artifacts/log"
+    export SCCACHE_ERROR_LOG="$scriptroot/../artifacts/log/sccache_debug.log"
+    export SCCACHE_LOG=debug
+    sccache --start-server
+    echo "sccache enabled for linux-x64 build"
+    sccache -s


The sccache presence check uses -f but the script immediately executes sccache. If the file exists but isn’t executable (or is the wrong binary), the build will fail (this script runs with set -e). Prefer checking -x and/or validating that invoking sccache --version succeeds before enabling it.

Suggested change

if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then

export PATH="$scriptroot/..:$PATH"

export USE_SCCACHE=true

export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache

export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"

export SCCACHE_AZURE_NO_CREDENTIALS=true

mkdir -p "$scriptroot/../artifacts/log"

export SCCACHE_ERROR_LOG="$scriptroot/../artifacts/log/sccache_debug.log"

export SCCACHE_LOG=debug

sccache --start-server

echo "sccache enabled for linux-x64 build"

sccache -s

if [[ "$os" == "linux" && "$arch" == "x64" && -x "$scriptroot/../sccache" ]]; then

if "$scriptroot/../sccache" --version >/dev/null 2>&1; then

export PATH="$scriptroot/..:$PATH"

export USE_SCCACHE=true

export SCCACHE_AZURE_BLOB_CONTAINER=runtime-cache

export SCCACHE_AZURE_CONNECTION_STRING="BlobEndpoint=https://runsccache.blob.core.windows.net"

export SCCACHE_AZURE_NO_CREDENTIALS=true

mkdir -p "$scriptroot/../artifacts/log"

export SCCACHE_ERROR_LOG="$scriptroot/../artifacts/log/sccache_debug.log"

export SCCACHE_LOG=debug

"$scriptroot/../sccache" --start-server

echo "sccache enabled for linux-x64 build"

"$scriptroot/../sccache" -s

fi

Copilot · 2026-02-07T09:00:35Z

eng/build.sh

+    sccache --start-server
+    echo "sccache enabled for linux-x64 build"
+    sccache -s
+fi


sccache --start-server and sccache -s will hard-fail the entire build if sccache can’t start or the remote backend isn’t reachable (because eng/build.sh runs with set -e). If sccache is intended to be a best-effort accelerator, wrap these invocations so failures don’t abort the build, and only emit stats when the server is actually running.

Test sccache with temp copy

c032b94

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Use portable binary

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Print sccache stats before running

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Use anonymous acces

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Typo

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Use sccache with anon backend support

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Also print stats at end

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agocke reopened this Feb 7, 2026

Remove everything except a single job for testing

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	export PATH="$scriptroot/..:$PATH"
	export SCCACHE_PATH="$scriptroot/../sccache"
	export PATH="$PATH:$scriptroot/.."

-    fi
-    sccache -s
+        if [[ -x "$scriptroot/../sccache" ]]; then
+            "$scriptroot/../sccache" -s || echo "Warning: failed to collect sccache stats"
+        else
+            echo "Warning: sccache binary at '$scriptroot/../sccache' is not executable; skipping sccache stats"
+        fi
+    fi

	sccache -s
	sccache -s \|\| echo "sccache stats are unavailable; continuing without cache stats"

		if [[ "$os" == "linux" && "$arch" == "x64" && -f "$scriptroot/../sccache" ]]; then
		export PATH="$scriptroot/..:$PATH"

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