ENH: Added computation of object file names that are almost always short enough to not exceed the filesystem path length limitation. This is useful when a source file from outside the tree is referenced with a long full path. The object file name previously would contain the entire path which when combined with the build output directory could exceed the filesystem limit. Now CMake recognizes this case and replaces enough of the beginning of the full path to the source file with an md5sum of the replaced portion to make the name fit on disk. This addresses bug#4520.

1 files changed, 89 insertions, 3 deletions

diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index e20bfe1..71d3c51 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -28,6 +28,11 @@
 #include "cmTest.h"
 #include "cmake.h"
 
+#if defined(CMAKE_BUILD_WITH_CMAKE)
+# define CM_LG_ENCODE_OBJECT_NAMES
+# include <cmsys/MD5.h>
+#endif
+
 #include <cmsys/System.h>
 
 #include <ctype.h> // for isalpha
@@ -2376,8 +2381,81 @@ cmLocalGenerator
     }
 }
 
+#if defined(CM_LG_ENCODE_OBJECT_NAMES)
+static std::string cmLocalGeneratorMD5(const char* input)
+{
+  char md5out[32];
+  cmsysMD5* md5 = cmsysMD5_New();
+  cmsysMD5_Initialize(md5);
+  cmsysMD5_Append(md5, reinterpret_cast<unsigned char const*>(input), -1);
+  cmsysMD5_FinalizeHex(md5, md5out);
+  cmsysMD5_Delete(md5);
+  return std::string(md5out, 32);
+}
+
+static bool
+cmLocalGeneratorShortenObjectName(std::string& objName,
+                                  std::string::size_type max_len)
+{
+  // Replace the beginning of the path portion of the object name with
+  // its own md5 sum.
+  std::string::size_type pos = objName.find('/', objName.size()-max_len+32);
+  if(pos != objName.npos)
+    {
+    std::string md5name = cmLocalGeneratorMD5(objName.substr(0, pos).c_str());
+    md5name += objName.substr(pos);
+    objName = md5name;
+
+    // The object name is now short enough.
+    return true;
+    }
+  else
+    {
+    // The object name could not be shortened enough.
+    return false;
+    }
+}
+
+static bool cmLocalGeneratorCheckObjectName(std::string& objName,
+                                            std::string::size_type dir_len)
+{
+  // Choose a maximum file name length.
+#if defined(_WIN32) || defined(__CYGWIN__)
+  std::string::size_type const max_total_len = 250;
+#else
+  std::string::size_type const max_total_len = 1000;
+#endif
+
+  // Enforce the maximum file name length if possible.
+  std::string::size_type max_obj_len = max_total_len;
+  if(dir_len < max_total_len)
+    {
+    max_obj_len = max_total_len - dir_len;
+    if(objName.size() > max_obj_len)
+      {
+      // The current object file name is too long.  Try to shorten it.
+      return cmLocalGeneratorShortenObjectName(objName, max_obj_len);
+      }
+    else
+      {
+      // The object file name is short enough.
+      return true;
+      }
+    }
+  else
+    {
+    // The build directory in which the object will be stored is
+    // already too deep.
+    return false;
+    }
+}
+#endif
+
 //----------------------------------------------------------------------------
-std::string& cmLocalGenerator::CreateSafeUniqueObjectFileName(const char* sin)
+std::string&
+cmLocalGenerator
+::CreateSafeUniqueObjectFileName(const char* sin,
+                                 std::string::size_type dir_len)
 {
   // Look for an existing mapped name for this object file.
   std::map<cmStdString,cmStdString>::iterator it =
@@ -2435,6 +2513,12 @@ std::string& cmLocalGenerator::CreateSafeUniqueObjectFileName(const char* sin)
       while ( !done );
       }
 
+#if defined(CM_LG_ENCODE_OBJECT_NAMES)
+    cmLocalGeneratorCheckObjectName(ssin, dir_len);
+#else
+    (void)dir_len;
+#endif
+
     // Insert the newly mapped object file name.
     std::map<cmStdString, cmStdString>::value_type e(sin, ssin);
     it = this->UniqueObjectNamesMap.insert(e).first;
@@ -2446,7 +2530,9 @@ std::string& cmLocalGenerator::CreateSafeUniqueObjectFileName(const char* sin)
 
 //----------------------------------------------------------------------------
 std::string
-cmLocalGenerator::GetObjectFileNameWithoutTarget(const cmSourceFile& source)
+cmLocalGenerator
+::GetObjectFileNameWithoutTarget(const cmSourceFile& source,
+                                 std::string::size_type dir_len)
 {
   // Construct the object file name using the full path to the source
   // file which is its only unique identification.
@@ -2517,7 +2603,7 @@ cmLocalGenerator::GetObjectFileNameWithoutTarget(const cmSourceFile& source)
     }
 
   // Convert to a safe name.
-  return this->CreateSafeUniqueObjectFileName(objectName.c_str());
+  return this->CreateSafeUniqueObjectFileName(objectName.c_str(), dir_len);
 }
 
 //----------------------------------------------------------------------------