cmDepends: merge dependers of depend makefile

Since one depender has multiple dependees, depend makefile generated
same depender line by line, to reduce file size and refine make file
parse speed, merge same dependers to one. And add a testcase for
large depend.make which generated source file includes 20000 header
files and run build and incremental build

Signed-off-by: Wangkai <wangkai86@huawei.com>
Signed-off-by: Zhaoyingdong <zhaoyingdong@huawei.com>

1 files changed, 22 insertions, 9 deletions

diff --git a/Source/cmDependsC.cxx b/Source/cmDependsC.cxx
index e6aef92..60e8cbf 100644
--- a/Source/cmDependsC.cxx
+++ b/Source/cmDependsC.cxx
@@ -7,6 +7,7 @@
 #include "cmsys/FStream.hxx"
 
 #include "cmFileTime.h"
+#include "cmGlobalUnixMakefileGenerator3.h"
 #include "cmLocalUnixMakefileGenerator3.h"
 #include "cmMakefile.h"
 #include "cmProperty.h"
@@ -215,16 +216,28 @@ bool cmDependsC::WriteDependencies(const std::set<std::string>& sources,
   // directory.  We must do the same here.
   std::string obj_m = this->LocalGenerator->ConvertToMakefilePath(obj_i);
   internalDepends << obj_i << '\n';
-
-  for (std::string const& dep : dependencies) {
-    makeDepends << obj_m << ": "
-                << this->LocalGenerator->ConvertToMakefilePath(
-                     this->LocalGenerator->MaybeConvertToRelativePath(binDir,
-                                                                      dep))
-                << '\n';
-    internalDepends << ' ' << dep << '\n';
+  if (!dependencies.empty()) {
+    const auto& lineContinue = static_cast<cmGlobalUnixMakefileGenerator3*>(
+                                 this->LocalGenerator->GetGlobalGenerator())
+                                 ->LineContinueDirective;
+    bool supportLongLineDepend = static_cast<cmGlobalUnixMakefileGenerator3*>(
+                                   this->LocalGenerator->GetGlobalGenerator())
+                                   ->SupportsLongLineDependencies();
+    if (supportLongLineDepend) {
+      makeDepends << obj_m << ':';
+    }
+    for (std::string const& dep : dependencies) {
+      std::string dependee = this->LocalGenerator->ConvertToMakefilePath(
+        this->LocalGenerator->MaybeConvertToRelativePath(binDir, dep));
+      if (supportLongLineDepend) {
+        makeDepends << ' ' << lineContinue << ' ' << dependee;
+      } else {
+        makeDepends << obj_m << ": " << dependee << '\n';
+      }
+      internalDepends << ' ' << dep << '\n';
+    }
+    makeDepends << '\n';
   }
-  makeDepends << '\n';
 
   return true;
 }