prevent C++ locale number formatting in text APIs (try 3)

This time it is the formatting of floating numbers in progress
reporting with a radix charater potentially not being dot.

Followup of 7303e11ff28f920a6277c159aa46f80c007350bb. Regression of
b58e2c7c56b1416a343e81f9f80cb1f02c128e25 in so far as it exchanging
very effected with slightly less effected code.

LP: 1611010

1 files changed, 5 insertions, 2 deletions

diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index 29362fb40..1efb772b4 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -1258,8 +1258,11 @@ bool pkgAcquireStatus::Pulse(pkgAcquire *Owner)
 	 snprintf(msg,sizeof(msg), _("Retrieving file %li of %li"), i, TotalItems);
 
       // build the status str
-      std::string dlstatus;
-      strprintf(dlstatus, "dlstatus:%ld:%.4f:%s\n", i, Percent, msg);
+      std::ostringstream str;
+      str.imbue(std::locale("C.UTF-8"));
+      str.precision(4);
+      str << "dlstatus" << ':' << std::fixed << i << ':' << Percent << ':' << msg << '\n';
+      auto const dlstatus = str.str();
       FileFd::Write(fd, dlstatus.data(), dlstatus.size());
    }