Don't add '-j' argument if parallelJobs <= 1

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 1.9.1
 Bug fixes:
 - Fix presets using conditions with macros and inheritance. [#2185](https://github.com/microsoft/vscode-cmake-tools/issues/2185)
+- Don't add `-j` argument when `cmake.parallelJobs` is set to `1`. [#2187](https://github.com/microsoft/vscode-cmake-tools/issues/2187) [@mark-ulrich](https://github.com/mark-ulrich)
 
 ## 1.9.0
 Improvements:

docs/cmake-settings.md

@@ -29,7 +29,7 @@ Options that support substitution, in the table below, allow variable references
 | `cmake.installPrefix` | If specified, sets a value for `CMAKE_INSTALL_PREFIX` when running CMake configure. If not set, no value will be passed.</br>If `CMAKE_INSTALL_PREFIX` is set via `cmake.configureArgs` or `cmake.configureSettings`, `cmake.installPrefix` will be ignored.| `null` (no value specified) | yes |
 | `cmake.loggingLevel` | A string setting that specifies how much output CMake Tools produces in its output channel. Set to one of `"trace"`, `"debug"`, `"info"`, `"note"`, `"warning"`, `"error"`, or `"fatal"`. `"trace"` is the most verbose.</br></br>Regardless of the logging level, CMake Tools writes all levels of logging to the CMake Tools log file. This file is useful if you need to [troubleshoot CMake Tools](troubleshoot.md) | `"info"` | no |
 | `cmake.mingwSearchDirs`| List of paths to search for a MinGW installation. This means that GCC does not need to be on your `$PATH` for it to be found via kit scanning. | ["C:\\MinGW"] (Search in C:\MinGW for a MinGW installation) | no |
-| `cmake.parallelJobs` | Specify  the number of jobs run in parallel during the build. | | no |
+| `cmake.parallelJobs` | Specify the number of jobs run in parallel during the build. Using the value `1` will disable build parallelism. | | no |
 | `cmake.preferredGenerators` | A list of strings of generator names to try, in order, when configuring a CMake project for the first time. | | no |
 | `cmake.saveBeforeBuild` | If `true` (the default), saves open text documents when build or configure is invoked before running CMake. | `true` | no |
 | `cmake.sourceDirectory` | Directory where the root `CMakeLists.txt` is stored. | `${workspaceFolder}` | yes |

package.nls.json

@@ -75,7 +75,7 @@
     "cmake-tools.configuration.cmake.configureArgs.description": "Additional arguments to pass to CMake when configuring.",
     "cmake-tools.configuration.cmake.buildArgs.description": "Additional arguments to pass to CMake when building.",
     "cmake-tools.configuration.cmake.buildToolArgs.description": "Additional arguments to pass to the underlying build tool when building.",
-    "cmake-tools.configuration.cmake.parallelJobs.description": "The number of parallel build jobs. Use zero to automatically detect the number of CPUs.",
+    "cmake-tools.configuration.cmake.parallelJobs.description": "The number of parallel build jobs. Use zero to automatically detect the number of CPUs. Setting this to 1 will disable build parallelism.",
     "cmake-tools.configuration.cmake.ctestPath.description": "Path to CTest executable. If null, will be inferred from cmake.cmakePath (recommended to leave null).",
     "cmake-tools.configuration.cmake.ctest.parallelJobs.description": "The number of parallel test jobs. Use zero to use the value of cmake.parallelJobs.",
     "cmake-tools.configuration.cmake.parseBuildDiagnostics.description": "Parse compiler output for warnings and errors.",

src/drivers/driver.ts

@@ -1564,19 +1564,22 @@ export abstract class CMakeDriver implements vscode.Disposable {
       const buildArgs: string[] = this.config.buildArgs.slice(0);
       const buildToolArgs: string[] = ['--'].concat(this.config.buildToolArgs);
 
-      // Prefer using CMake's build options to set parallelism over tool-specific switches.
-      // The feature is not available until version 3.14.
-      if (this.cmake.version && util.versionGreaterOrEquals(this.cmake.version, util.parseVersion('3.14.0'))) {
-        buildArgs.push('-j');
-        if (this.config.numJobs) {
-          buildArgs.push(this.config.numJobs.toString());
-        }
-      } else {
-        if (gen) {
-          if (/(Unix|MinGW) Makefiles|Ninja/.test(gen) && targets !== ['clean']) {
-            buildToolArgs.push('-j', this.config.numJobs.toString());
-          } else if (/Visual Studio/.test(gen) &&  targets !== ['clean']) {
-            buildToolArgs.push('/maxcpucount:' + this.config.numJobs.toString());
+      // Only add '-j' argument if parallelJobs > 1
+      if (this.config.numJobs > 1) {
+        // Prefer using CMake's build options to set parallelism over tool-specific switches.
+        // The feature is not available until version 3.14.
+        if (this.cmake.version && util.versionGreaterOrEquals(this.cmake.version, util.parseVersion('3.14.0'))) {
+          buildArgs.push('-j');
+          if (this.config.numJobs) {
+            buildArgs.push(this.config.numJobs.toString());
+          }
+        } else {
+          if (gen) {
+            if (/(Unix|MinGW) Makefiles|Ninja/.test(gen) && targets !== ['clean']) {
+              buildToolArgs.push('-j', this.config.numJobs.toString());
+            } else if (/Visual Studio/.test(gen) &&  targets !== ['clean']) {
+              buildToolArgs.push('/maxcpucount:' + this.config.numJobs.toString());
+            }
           }
         }
       }