add utils::strdup() convenience function

doc/src/Developer_utils.rst

@@ -71,6 +71,9 @@ and parsing files or arguments.
 
 ----------
 
+.. doxygenfunction:: strdup
+   :project: progguide
+
 .. doxygenfunction:: trim
    :project: progguide
 

src/utils.cpp

@@ -546,6 +546,18 @@ int utils::expand_args(const char *file, int line, int narg, char **arg,
   return newarg;
 }
 
+/* ----------------------------------------------------------------------
+   Make copy of string in new storage. Works like the (non-portable)
+   C-style strdup() but also accepts a C++ string as argument.
+------------------------------------------------------------------------- */
+
+char *utils::strdup(const std::string &text)
+{
+  char *tmp = new char[text.size()+1];
+  strcpy(tmp,text.c_str());
+  return tmp;
+}
+
 /* ----------------------------------------------------------------------
    Return string without leading or trailing whitespace
 ------------------------------------------------------------------------- */

src/utils.h

@@ -195,6 +195,17 @@ namespace LAMMPS_NS {
     int expand_args(const char *file, int line, int narg, char **arg,
                     int mode, char **&earg, LAMMPS *lmp);
 
+    /** Make C-style copy of string in new storage
+     *
+     * This allocates a storage buffer and copies the C-style or
+     * C++ style string into it.  The buffer is allocated with "new"
+     * and thus needs to be deallocated with "delete[]".
+     *
+     * \param text  string that should be copied
+     * \return new buffer with copy of string */
+
+    char *strdup(const std::string &text);
+
     /** Trim leading and trailing whitespace. Like TRIM() in Fortran.
      *
      * \param line  string that should be trimmed

unittest/utils/test_utils.cpp

@@ -30,6 +30,21 @@ using ::testing::StrEq;
 #define FLERR __FILE__, __LINE__
 #endif
 
+TEST(Utils, strdup)
+{
+    std::string original("some_text");
+    const char *copy = utils::strdup(original);
+    ASSERT_THAT(original, StrEq(copy));
+    ASSERT_NE(copy,original.c_str());
+
+    const char *copy2 = utils::strdup(copy);
+    ASSERT_THAT(original, StrEq(copy2));
+    ASSERT_NE(copy,copy2);
+
+    delete[] copy;
+    delete[] copy2;
+}
+
 TEST(Utils, trim)
 {
     auto trimmed = utils::trim("\t some text");