Use a define and sizeof instead of multiple magic numbers

Author: jimhester

inst/include/cpp11/declarations.hpp

@@ -27,24 +27,26 @@ T& unmove(T&& t) {
   } while (false);
 #endif
 
-#define BEGIN_CPP11      \
-  SEXP err = R_NilValue; \
-  char buf[8192] = "";   \
+#define CPP11_ERROR_BUFSIZE 8192
+
+#define BEGIN_CPP11                   \
+  SEXP err = R_NilValue;              \
+  char buf[CPP11_ERROR_BUFSIZE] = ""; \
   try {
-#define END_CPP11                                        \
-  }                                                      \
-  catch (cpp11::unwind_exception & e) {                  \
-    err = e.token;                                       \
-  }                                                      \
-  catch (std::exception & e) {                           \
-    strncpy(buf, e.what(), 8192 - 1);                    \
-  }                                                      \
-  catch (...) {                                          \
-    strncpy(buf, "C++ error (unknown cause)", 8192 - 1); \
-  }                                                      \
-  if (buf[0] != '\0') {                                  \
-    Rf_errorcall(R_NilValue, "%s", buf);                 \
-  } else if (err != R_NilValue) {                        \
-    CPP11_UNWIND                                         \
-  }                                                      \
+#define END_CPP11                                           \
+  }                                                         \
+  catch (cpp11::unwind_exception & e) {                     \
+    err = e.token;                                          \
+  }                                                         \
+  catch (std::exception & e) {                              \
+    strncpy(buf, e.what(), sizeof(buf));                    \
+  }                                                         \
+  catch (...) {                                             \
+    strncpy(buf, "C++ error (unknown cause)", sizeof(buf)); \
+  }                                                         \
+  if (buf[0] != '\0') {                                     \
+    Rf_errorcall(R_NilValue, "%s", buf);                    \
+  } else if (err != R_NilValue) {                           \
+    CPP11_UNWIND                                            \
+  }                                                         \
   return R_NilValue;