Merge branch 'abi_comp' into 4.1

* abi_comp:
  restore CatchSignals to fix API compatibility
  fix build

src/api/baseapi.cpp

@@ -253,6 +253,25 @@ size_t TessBaseAPI::getOpenCLDevice(void **data) {
   return 0;
 }
 
+/**
+ * Writes the thresholded image to stderr as a PBM file on receipt of a
+ * SIGSEGV, SIGFPE, or SIGBUS signal. (Linux/Unix only).
+ */
+void TessBaseAPI::CatchSignals() {
+#ifdef __linux__
+  struct sigaction action;
+  memset(&action, 0, sizeof(action));
+  action.sa_handler = &signal_exit;
+  action.sa_flags = SA_RESETHAND;
+  sigaction(SIGSEGV, &action, nullptr);
+  sigaction(SIGFPE, &action, nullptr);
+  sigaction(SIGBUS, &action, nullptr);
+#else
+  // Warn API users that an implementation is needed.
+  tprintf("CatchSignals has no non-linux implementation!\n");
+#endif
+}
+
 /**
  * Set the name of the input file. Needed only for training and
  * loading a UNLV zone file.

src/api/baseapi.h

@@ -107,6 +107,12 @@ class TESS_API TessBaseAPI {
    */
   static size_t getOpenCLDevice(void **device);
 
+  /**
+   * Writes the thresholded image to stderr as a PBM file on receipt of a
+   * SIGSEGV, SIGFPE, or SIGBUS signal. (Linux/Unix only).
+   */
+  static void CatchSignals();
+
   /**
    * Set the name of the input file. Needed for training and
    * reading a UNLV zone file, and for searchable PDF output.

src/cutil/oldlist.cpp

@@ -61,6 +61,19 @@
 #include "errcode.h"    // for ASSERT_HOST
 #include "structures.h"
 
+/**********************************************************************
+ *  c o p y   f i r s t
+ *
+ *  Do the appropriate kind a push operation to copy the first node from
+ *  one list to another.
+ *
+ **********************************************************************/
+
+#define copy_first(l1,l2)  \
+(l2=push(l2, first_node(l1)))
+
+
+
 /*----------------------------------------------------------------------
               F u n c t i o n s
 ----------------------------------------------------------------------*/