Changed strip_outer_ld_preload to remove librrpreload in any case.

In test nested_detach (with an asan enabled rr build) following assertion
was hit because LD_PRELOAD contained libasan before librrpreload.

RecordSession.cc:2047: void rr::strip_outer_ld_preload(std::vector<std::__cxx11::basic_string<char> >&): Assertion `preload_pos == string::npos' failed.

src/RecordSession.cc

@@ -10,6 +10,7 @@
 #include <sys/socket.h>
 
 #include <algorithm>
+#include <iostream>
 #include <sstream>
 #include <string>
 
@@ -2030,24 +2031,29 @@ static void inject_ld_helper_library(vector<string>& env,
 }
 
 void strip_outer_ld_preload(vector<string>& env) {
- auto env_assignment = "LD_PRELOAD=";
+ string env_assignment = "LD_PRELOAD=";
  auto it = env.begin();
  for (; it != env.end(); ++it) {
  if (it->find(env_assignment) != 0) {
  continue;
  }
- size_t colon_pos = it->find(":");
- if (colon_pos != string::npos) {
- // If the preload library is loaded at all, it must be first
- size_t preload_pos = it->find("librrpreload");
- if (preload_pos < colon_pos) {
- string new_ld_preload = it->substr(++colon_pos);
- *it = env_assignment + new_ld_preload;
- return;
- } else {
- DEBUG_ASSERT(preload_pos == string::npos);
+ istringstream st = istringstream(it->substr(env_assignment.length()));
+ string new_ld_preload;
+ string lib;
+ while (getline(st, lib, ':')) {
+ if (lib.empty()) {
+ continue;
  }
+ if (lib.find("librrpreload") != string::npos) {
+ continue;
+ }
+ if (!new_ld_preload.empty()) {
+ new_ld_preload += ":";
+ }
+ new_ld_preload += lib;
  }
+ *it = env_assignment + new_ld_preload;
+ return;
  }
 }