internal/report: fall back to $GOROOT/src when locating source files

.github/workflows/ci.yaml

@@ -6,6 +6,10 @@ on:
   pull_request:
   schedule:
     - cron: '0 2 * * *' # Run every day, at 2AM UTC.
+
+permissions:
+  contents: read
+
 env:
   GOPATH: ${{ github.workspace }}
   WORKING_DIR: ./src/github.com/google/pprof/
@@ -18,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go: ['1.24', '1.25', 'tip']
+        go: ['1.25', '1.26']
         # Supported macOS versions can be found in
         # https://github.com/actions/virtual-environments#available-environments.
         os: ['macos-14', 'macos-15']
@@ -48,43 +52,19 @@ jobs:
 
     steps:
       - name: Checkout the repo
-        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           path: ${{ env.WORKING_DIR }}
 
       - name: Update Go version using setup-go
-        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
-        if: matrix.go != 'tip'
+        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
         with:
           # Include cache directives to allow proper caching. Without them, we
           # get setup-go "Restore cache failed" warnings.
           go-version: ${{ matrix.go }}
           cache: true
           cache-dependency-path: '**/go.sum'
 
-      - name: Install Go bootstrap compiler
-        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
-        if: matrix.go == 'tip'
-        with:
-          # Bootstrapping go tip requires 1.24
-          # Include cache directives to allow proper caching. Without them, we
-          # get setup-go "Restore cache failed" warnings.
-          go-version: 1.24
-          cache: true
-          cache-dependency-path: '**/go.sum'
-
-      - name: Update Go version manually
-        if: matrix.go == 'tip'
-        working-directory: ${{ github.workspace }}
-        run: |
-          git clone https://go.googlesource.com/go $HOME/gotip
-          cd $HOME/gotip/src
-          ./make.bash
-          echo "GOROOT=$HOME/gotip" >> $GITHUB_ENV
-          echo "RUN_STATICCHECK=false" >> $GITHUB_ENV
-          echo "RUN_GOLANGCI_LINTER=false" >> $GITHUB_ENV
-          echo "$HOME/gotip/bin:$PATH" >> $GITHUB_PATH
-
       - name: Set up Xcode
         uses: maxim-lobanov/setup-xcode@ed7a3b1fda3918c0306d1b724322adc0b8cc0a90 # v1.7.0
         with:
@@ -120,47 +100,23 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go: ['1.24', '1.25', 'tip']
+        go: ['1.25', '1.26']
         os: ['ubuntu-24.04', 'ubuntu-22.04']
     steps:
       - name: Checkout the repo
-        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           path: ${{ env.WORKING_DIR }}
 
       - name: Update Go version using setup-go
-        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
-        if: matrix.go != 'tip'
+        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
         with:
           # Include cache directives to allow proper caching. Without them, we
           # get setup-go "Restore cache failed" warnings.
           go-version: ${{ matrix.go }}
           cache: true
           cache-dependency-path: '**/go.sum'
 
-      - name: Install Go bootstrap compiler
-        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
-        if: matrix.go == 'tip'
-        with:
-          # Bootstrapping go tip requires 1.24
-          # Include cache directives to allow proper caching. Without them, we
-          # get setup-go "Restore cache failed" warnings.
-          go-version: 1.24
-          cache: true
-          cache-dependency-path: '**/go.sum'
-
-      - name: Update Go version manually
-        if: matrix.go == 'tip'
-        working-directory: ${{ github.workspace }}
-        run: |
-          git clone https://go.googlesource.com/go $HOME/gotip
-          cd $HOME/gotip/src
-          ./make.bash
-          echo "GOROOT=$HOME/gotip" >> $GITHUB_ENV
-          echo "RUN_STATICCHECK=false" >> $GITHUB_ENV
-          echo "RUN_GOLANGCI_LINTER=false" >> $GITHUB_ENV
-          echo "$HOME/gotip/bin" >> $GITHUB_PATH
-
       - name: Check chrome for browser tests
         run: |
           google-chrome --version
@@ -214,15 +170,15 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go: ['1.24', '1.25']
+        go: ['1.25', '1.26']
     steps:
       - name: Checkout the repo
-        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           path: ${{ env.WORKING_DIR }}
 
       - name: Update Go version using setup-go
-        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
+        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
         with:
           # Include cache directives to allow proper caching. Without them, we
           # get setup-go "Restore cache failed" warnings.

browsertests/go.mod

@@ -1,8 +1,6 @@
 module github.com/google/pprof/browsertests
 
-go 1.24.0
-
-toolchain go1.24.9
+go 1.25.0
 
 // Use the version of pprof in this directory tree.
 replace github.com/google/pprof => ../

go.mod

@@ -1,8 +1,6 @@
 module github.com/google/pprof
 
-go 1.24.0
-
-toolchain go1.24.9
+go 1.25.0
 
 require (
 	github.com/chzyer/readline v1.5.1

internal/report/source.go

@@ -25,6 +25,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"slices"
 	"sort"
 	"strconv"
@@ -1007,28 +1008,95 @@ func openSourceFile(path, searchPath, trim string) (*os.File, error) {
 	path = trimPath(path, trim, searchPath)
 	// If file is still absolute, require file to exist.
 	if filepath.IsAbs(path) {
-		f, err := os.Open(path)
-		return f, err
-	}
-	// Scan each component of the path.
-	for _, dir := range filepath.SplitList(searchPath) {
-		// Search up for every parent of each possible path.
-		for {
-			filename := filepath.Join(dir, path)
-			if f, err := os.Open(filename); err == nil {
-				return f, nil
-			}
-			parent := filepath.Dir(dir)
-			if parent == dir {
-				break
+		if f, err := tryOpenFile(path); err == nil {
+			return f, nil
+		}
+	} else {
+		// Scan each component of the path.
+		for _, dir := range filepath.SplitList(searchPath) {
+			// Search up for every parent of each possible path.
+			for {
+				filename := filepath.Join(dir, path)
+				if f, err := tryOpenFile(filename); err == nil {
+					return f, nil
+				}
+				parent := filepath.Dir(dir)
+				if parent == dir {
+					break
+				}
+				dir = parent
 			}
-			dir = parent
 		}
 	}
+	// Fall back to looking for Go standard library sources under the local
+	// $GOROOT/src, since profiles from Go programs refer to standard library
+	// files under the GOROOT of the machine where the program was built.
+	if f, err := openGorootSourceFile(path, gorootSrc); err == nil {
+		return f, nil
+	}
 
 	return nil, fmt.Errorf("could not find file %s on path %s", path, searchPath)
 }
 
+// tryOpenFile opens the file at filename if it exists and is not a directory,
+// which os.Open would also happily open.
+func tryOpenFile(filename string) (*os.File, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	stat, err := f.Stat()
+	if err != nil {
+		f.Close()
+		return nil, err
+	}
+	if stat.IsDir() {
+		f.Close()
+		return nil, fmt.Errorf("%s is a directory", filename)
+	}
+	return f, nil
+}
+
+// gorootSrc is the directory holding the Go standard library sources, if
+// known. runtime.GOROOT honors the $GOROOT environment variable and otherwise
+// reports the GOROOT this binary was built with, which is the Go installation
+// used to `go install` pprof in the common case.
+var gorootSrc = func() string {
+	if goroot := runtime.GOROOT(); goroot != "" {
+		return filepath.Join(goroot, "src")
+	}
+	return ""
+}()
+
+// openGorootSourceFile tries to open a Go standard library source file under
+// gorootSrc. Binaries built without -trimpath record standard library files
+// under the build machine's GOROOT (e.g. /usr/local/go/src/runtime/proc.go),
+// which may not exist locally, so resolve the path components after a "/src/"
+// component against gorootSrc. Binaries built with -trimpath record them
+// relative to $GOROOT/src (e.g. runtime/proc.go), so resolve relative paths
+// against gorootSrc directly.
+func openGorootSourceFile(path, gorootSrc string) (*os.File, error) {
+	if gorootSrc == "" {
+		return nil, fmt.Errorf("GOROOT is not known")
+	}
+	if !filepath.IsAbs(path) {
+		if f, err := tryOpenFile(filepath.Join(gorootSrc, path)); err == nil {
+			return f, nil
+		}
+	}
+	sPath := filepath.ToSlash(path)
+	for {
+		i := strings.Index(sPath, "/src/")
+		if i == -1 {
+			return nil, fmt.Errorf("could not find file %s under %s", path, gorootSrc)
+		}
+		sPath = sPath[i+len("/src/"):]
+		if f, err := tryOpenFile(filepath.Join(gorootSrc, filepath.FromSlash(sPath))); err == nil {
+			return f, nil
+		}
+	}
+}
+
 // trimPath cleans up a path by removing prefixes that are commonly
 // found on profiles plus configured prefixes.
 // TODO(aalexand): Consider optimizing out the redundant work done in this