Feature : Enable LLDB Debugging for R Dev Container

.devcontainer/devcontainer.json

@@ -4,6 +4,9 @@
     "hostRequirements": {
         "cpus": 4
     },
+    "runArgs": [
+    "--cap-add=SYS_PTRACE"
+    ],
     "customizations": {
         "vscode": {
             "settings": {
@@ -12,8 +15,11 @@
                 "editor.detectIndentation": false,
                 "r.lsp.diagnostics": false,
                 "r.plot.useHttpgd": true,
+                "r.rterm.linux": "/workspaces/r-dev-env/scripts/launch_r.sh",
                 "r.rpath.linux": "/usr/bin/R",
-                "r.rterm.linux": "/usr/bin/R",
+                "terminal.integrated.env.linux": {
+                    "R_RPATH_LINUX": "${config:r.rpath.linux}"
+                },
                 "terminal.integrated.sendKeybindingsToShell": true,
                 "svn.multipleFolders.enabled": true,
                 "workbench.editorAssociations": {
@@ -28,9 +34,10 @@
                 "johnstoncode.svn-scm",
                 "ms-vscode.cpptools",
                 "MS-vsliveshare.vsliveshare",
-                "natqe.reload"
+                "natqe.reload",
+                "vadimcn.vscode-lldb"
             ]
         }
     },
-    "postCreateCommand": "find . -wholename '*.git*'  -type d -prune -o -type f -exec chown vscode:vscode {} \\; && sh /workspaces/r-dev-env/scripts/localscript.sh"
+"postCreateCommand": "find . -wholename '.git*' -type d -prune -o -type f -exec chown vscode:vscode {} \\; && sh ./scripts/localscript.sh"
 }

.devcontainer/launch.json

@@ -0,0 +1,22 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Debug R (C debugging)",
+      "type": "cppdbg",
+      "request": "launch",
+      "program": "/workspaces/r-dev-env/scripts/launch_r.sh",
+      "args": [],
+      "stopAtEntry": false,
+      "cwd": "${workspaceFolder}",
+      "environment": [
+        {
+          "name": "R_RPATH_LINUX",
+          "value": "${config:r.rpath.linux}"
+        }
+      ],
+      "externalConsole": false,
+      "MIMode": "lldb"
+    }
+  ]
+}

docs/tutorials/building_r.md

@@ -55,7 +55,22 @@ mkdir -p $BUILDDIR
 cd $BUILDDIR
 ```
 
-**5) Configure the build**
+**5) Set CFLAGS (Optional—For Debugging C Code)**
+
+- **This step is optional and recommended for those who want to debug C code.**
+- Set the `CFLAGS` environment variable before running configure:
+
+```bash
+CFLAGS="-g -O0"
+```
+
+- These flags modify the configuration defined in the next step,
+so that when R is built, C code will be compiled with debugging
+symbols (`-g`) and compiler optimizations will be disabled
+(`-O0`) so that the structure of the code closely matches the
+original source.
+
+**6) Configure the build**
 
 - After we change directory, we must run the configure script from the source
 directory.  This step takes ~1 minute on the codespace.
@@ -80,7 +95,7 @@ $TOP_SRCDIR/configure --with-valgrind-instrumentation=1
 
     ![alt text](../assets/rdev7.png)
 
-**6) Build R**
+**7) Build R**
 
 Having configured R, we run `make` to build R. This take 5-10 minutes on the
 codespace.
@@ -89,7 +104,7 @@ codespace.
 make
 ```
 
-**7) Check R**
+**8) Check R**
 
 Check that the build of R passes R's standard checks:
 
@@ -101,7 +116,7 @@ This takes a couple of minutes in the codespace. The check will stop with a
 error message if any of the tests fail. If this happens, see [SVN
 Help](./svn_help.md) for how to revert to a version that passes check.
 
-**8) Make R terminals use the built R**
+**9) Make R terminals use the built R**
 
 Run the `which_r` script to set which R to use for R terminals in VSCode. When
 prompted, enter the number corresponding to `r-devel`
@@ -125,7 +140,7 @@ built![^1]
 selected version is saved in the VSCode settings, so will be saved when you stop
 and restart the codespace.
 
-**9) Make contributions**
+**10) Make contributions**
 
 - After having built the current development version of R, we can now make
   changes to the source code and contribute to the project.

scripts/allow_ptrace.c

@@ -0,0 +1,6 @@
+#include <sys/prctl.h>
+
+__attribute__((constructor))
+static void allow_ptrace(void) {
+    prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
+}

scripts/launch_r.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# Preload helper for ptrace
+export LD_PRELOAD="$(dirname "$0")/allow_ptrace.so"
+
+# VS Code sets the env var R_RPATH_LINUX to the path from r.rpath.linux
+if [ -n "${R_RPATH_LINUX:-}" ] && [ -x "$R_RPATH_LINUX" ]; then
+  R_BINARY="$R_RPATH_LINUX"
+else
+  R_BINARY="/usr/bin/R"
+fi
+
+exec "$R_BINARY" "$@"

scripts/localscript.sh

@@ -9,21 +9,21 @@ local_script(){
 WORK_DIR=$PWD
 VSCODE_DIR="$WORK_DIR/.vscode"
 DEVCONTAINER_JSON="$WORK_DIR/.devcontainer/devcontainer.json"
+SCRIPTS_DIR="$WORK_DIR/scripts"
 
 # Create patch directory in workspace root ($PWD at start)
 PATCHDIR="$WORK_DIR/patches"
 mkdir -p $PATCHDIR
 mkdir -p $VSCODE_DIR
 
 # Copy the which_r and set_build_r function definitions to .bashrc
-cat $WORK_DIR/scripts/which_r.sh >> ~/.bashrc
-cat $WORK_DIR/scripts/set_build_r.sh >> ~/.bashrc
+cat $SCRIPTS_DIR/which_r.sh >> ~/.bashrc
+cat $SCRIPTS_DIR/set_build_r.sh >> ~/.bashrc
 
 # Copy over the welcome message script to be run when bash terminal starts
-cat $WORK_DIR/scripts/welcome_msg.sh >> ~/.bashrc
+cat $SCRIPTS_DIR/welcome_msg.sh >> ~/.bashrc
 
 #bash ~/.bashrc
-
 # Remove git directory if it exists
 rm -rf .git
 
@@ -38,3 +38,13 @@ fi
 
 # Run the main function
 local_script
+
+# Remove the .vscode/settings.json file if it exists so that
+# it does not interfere with the devcontainer.json
+rm -f "$WORK_DIR/.vscode/settings.json"
+
+# 1. Build the ptrace helper library
+gcc -shared -fPIC -o "$SCRIPTS_DIR/allow_ptrace.so" "$SCRIPTS_DIR/allow_ptrace.c"
+
+# 2. Mark the wrapper executable
+chmod +x "$SCRIPTS_DIR/launch_r.sh"

scripts/which_r.sh

@@ -60,7 +60,7 @@ which_r() {
   fi
 
   # Update settings.json with the chosen R path
-  updated_settings_data=$(cat "$settings_file_path" | jq --arg subdir "$selected_version" '."r.rterm.linux"=$subdir | ."r.rpath.linux"=$subdir')
+  updated_settings_data=$(cat "$settings_file_path" | jq --arg subdir "$selected_version" '."r.rpath.linux"=$subdir')
   echo "$updated_settings_data" > "$settings_file_path"
 
   echo "R terminal will now use version: $selected_version"