Cpp module: Allow a set of source files to be combined into one

We introduce file tags and properties to support the concept of
"amalgamation builds" for C, C++, Objective-C and Objective-C++.

[ChangeLog] Provided the means to easily combine source files for the C
language family in order to support "amalgamation builds".

Change-Id: Ia3d248203c29418907178b47dba84ca3a18a0857
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

2 files changed, 92 insertions, 4 deletions

diff --git a/share/qbs/imports/qbs/ModUtils/utils.js b/share/qbs/imports/qbs/ModUtils/utils.js
index 8fb8b7cb0..046e8adac 100644
--- a/share/qbs/imports/qbs/ModUtils/utils.js
+++ b/share/qbs/imports/qbs/ModUtils/utils.js
@@ -33,8 +33,20 @@ var File = require("qbs.File");
 var FileInfo = require("qbs.FileInfo");
 var Process = require("qbs.Process");
 var TemporaryDir = require("qbs.TemporaryDir");
+var TextFile = require("qbs.TextFile");
 var Utilities = require("qbs.Utilities");
 
+function mergeCFiles(inputs, outputFilePath)
+{
+    var f = new TextFile(outputFilePath, TextFile.WriteOnly);
+    try {
+        for (var i = 0; i < inputs.length; ++i)
+            f.writeLine('#include "' + inputs[i].filePath + '"');
+    } finally {
+        f.close();
+    }
+}
+
 function sanitizedList(list, product, fullPropertyName) {
     if (!Array.isArray(list))
         return list;
diff --git a/share/qbs/modules/cpp/CppModule.qbs b/share/qbs/modules/cpp/CppModule.qbs
index dd36cc228..150d773e1 100644
--- a/share/qbs/modules/cpp/CppModule.qbs
+++ b/share/qbs/modules/cpp/CppModule.qbs
@@ -312,24 +312,100 @@ Module {
 
     property bool allowUnresolvedSymbols: false
 
+    property bool combineCSources: false
+    property bool combineCxxSources: false
+    property bool combineObjcSources: false
+    property bool combineObjcxxSources: false
+
+    // TODO: The following four rules could use a convenience base item if rule properties
+    //       were available in Artifact items and prepare scripts.
+    Rule {
+        multiplex: true
+        inputs: ["c.combine"]
+        Artifact {
+            filePath: "amalgamated_" + product.targetName + ".c"
+            fileTags: ["c"]
+        }
+        prepare: {
+            var cmd = new JavaScriptCommand();
+            cmd.description = "creating " + output.fileName;
+            cmd.highlight = "codegen";
+            cmd.sourceCode = function() {
+                ModUtils.mergeCFiles(inputs["c.combine"], output.filePath);
+            };
+            return [cmd];
+        }
+    }
+    Rule {
+        multiplex: true
+        inputs: ["cpp.combine"]
+        Artifact {
+            filePath: "amalgamated_" + product.targetName + ".cpp"
+            fileTags: ["cpp"]
+        }
+        prepare: {
+            var cmd = new JavaScriptCommand();
+            cmd.description = "creating " + output.fileName;
+            cmd.highlight = "codegen";
+            cmd.sourceCode = function() {
+                ModUtils.mergeCFiles(inputs["cpp.combine"], output.filePath);
+            };
+            return [cmd];
+        }
+    }
+    Rule {
+        multiplex: true
+        inputs: ["objc.combine"]
+        Artifact {
+            filePath: "amalgamated_" + product.targetName + ".m"
+            fileTags: ["objc"]
+        }
+        prepare: {
+            var cmd = new JavaScriptCommand();
+            cmd.description = "creating " + output.fileName;
+            cmd.highlight = "codegen";
+            cmd.sourceCode = function() {
+                ModUtils.mergeCFiles(inputs["objc.combine"], output.filePath);
+            };
+            return [cmd];
+        }
+    }
+    Rule {
+        multiplex: true
+        inputs: ["objcpp.combine"]
+        Artifact {
+            filePath: "amalgamated_" + product.targetName + ".mm"
+            fileTags: ["objccpp"]
+        }
+        prepare: {
+            var cmd = new JavaScriptCommand();
+            cmd.description = "creating " + output.fileName;
+            cmd.highlight = "codegen";
+            cmd.sourceCode = function() {
+                ModUtils.mergeCFiles(inputs["objcpp.combine"], output.filePath);
+            };
+            return [cmd];
+        }
+    }
+
     FileTagger {
         patterns: ["*.c"]
-        fileTags: ["c"]
+        fileTags: combineCSources ? ["c.combine"] : ["c"]
     }
 
     FileTagger {
         patterns: ["*.C", "*.cpp", "*.cxx", "*.c++", "*.cc"]
-        fileTags: ["cpp"]
+        fileTags: combineCxxSources ? ["cpp.combine"] : ["cpp"]
     }
 
     FileTagger {
         patterns: ["*.m"]
-        fileTags: ["objc"]
+        fileTags: combineObjcSources ? ["objc.combine"] : ["objc"]
     }
 
     FileTagger {
         patterns: ["*.mm"]
-        fileTags: ["objcpp"]
+        fileTags: combineObjcxxSources ? ["objcpp.combine"] : ["objcpp"]
     }
 
     FileTagger {