Merge pull request #154 from dpacbach/master

Allow specifying list of source file search paths in environment var

backward.hpp

@@ -397,6 +397,16 @@ template <typename T> T &move(T &v) { return v; }
 } // namespace backward
 #endif // BACKWARD_ATLEAST_CXX11
 
+namespace backward {
+namespace details {
+#if defined(BACKWARD_SYSTEM_WINDOWS)
+const char kBackwardPathDelimiter[] = ";";
+#else
+const char kBackwardPathDelimiter[] = ":";
+#endif
+} // namespace details
+} // namespace backward
+
 namespace backward {
 
 namespace system_tag {
@@ -587,6 +597,29 @@ template <> struct demangler_impl<system_tag::current_tag> {
 
 struct demangler : public demangler_impl<system_tag::current_tag> {};
 
+// Split a string on the platform's PATH delimiter.  Example: if delimiter
+// is ":" then:
+//   ""              --> []
+//   ":"             --> ["",""]
+//   "::"            --> ["","",""]
+//   "/a/b/c"        --> ["/a/b/c"]
+//   "/a/b/c:/d/e/f" --> ["/a/b/c","/d/e/f"]
+//   etc.
+inline std::vector<std::string> split_source_prefixes(const std::string &s) {
+  std::vector<std::string> out;
+  size_t last = 0;
+  size_t next = 0;
+  size_t delimiter_size = sizeof(kBackwardPathDelimiter)-1;
+  while ((next = s.find(kBackwardPathDelimiter, last)) != std::string::npos) {
+    out.push_back(s.substr(last, next-last));
+    last = next + delimiter_size;
+  }
+  if (last <= s.length()) {
+    out.push_back(s.substr(last));
+  }
+  return out;
+}
+
 } // namespace details
 
 /*************** A TRACE ***************/
@@ -3360,8 +3393,22 @@ class SourceFile {
   typedef std::vector<std::pair<unsigned, std::string>> lines_t;
 
   SourceFile() {}
-  SourceFile(const std::string &path)
-      : _file(new std::ifstream(path.c_str())) {}
+  SourceFile(const std::string &path) {
+    // 1. If BACKWARD_CXX_SOURCE_PREFIXES is set then assume it contains
+    //    a colon-separated list of path prefixes.  Try prepending each
+    //    to the given path until a valid file is found.
+    const std::vector<std::string>& prefixes = get_paths_from_env_variable();
+    for (size_t i = 0; i < prefixes.size(); ++i) {
+      // Double slashes (//) should not be a problem.
+      std::string new_path = prefixes[i] + '/' + path;
+      _file.reset(new std::ifstream(new_path.c_str()));
+      if (is_open()) break;
+    }
+    // 2. If no valid file found then fallback to opening the path as-is.
+    if (!_file || !is_open()) {
+      _file.reset(new std::ifstream(path.c_str()));
+    }
+  }
   bool is_open() const { return _file->is_open(); }
 
   lines_t &get_lines(unsigned line_start, unsigned line_count, lines_t &lines) {
@@ -3457,6 +3504,20 @@ class SourceFile {
   details::handle<std::ifstream *, details::default_delete<std::ifstream *>>
       _file;
 
+  std::vector<std::string> get_paths_from_env_variable_impl() {
+    std::vector<std::string> paths;
+    const char* prefixes_str = std::getenv("BACKWARD_CXX_SOURCE_PREFIXES");
+    if (prefixes_str && prefixes_str[0]) {
+      paths = details::split_source_prefixes(prefixes_str);
+    }
+    return paths;
+  }
+
+  const std::vector<std::string>& get_paths_from_env_variable() {
+    static std::vector<std::string> paths = get_paths_from_env_variable_impl();
+    return paths;
+  }
+
 #ifdef BACKWARD_ATLEAST_CXX11
   SourceFile(const SourceFile &) = delete;
   SourceFile &operator=(const SourceFile &) = delete;