yhttpd: port ychat fixes, get it building + stable in Docker (task 9s0)

Ports the ychat revival fixes (unsigned/size_t npos truncation, ofstream
== NULL, tool::trim OOB, CGI popen -> execve, www.yChat.org links, g++
version gate, config.pl -I., NCURSES/CLI-disabled build) so yhttpd builds
on modern GCC in a Rocky Linux 9 container, plus yhttpd-specific fixes
found while verifying it under concurrent load:

- listen() backlog was hardcoded to 1; bumped to SOMAXCONN.
- sock::_close() closed sockets with unread request bytes still in the
  kernel receive buffer (read_http() only reads the GET line), so Linux
  sent an abortive RST instead of a FIN, racing the client's read of the
  response ("connection reset by peer" even though it was delivered).
  Fixed with a non-blocking, bounded drain before close() - confirmed via
  tcpdump: RSTs on every response before, zero after, across 140+
  requests / concurrent bursts of 20.
- Removed a duplicate _make_server_socket() call in start() (wrap.cpp's
  init_wrapper() already makes it before start() runs) that leaked a fd
  and would have double-initialized SSL if OPENSSL is ever enabled;
  caught by fresh-context review, documented honestly in DOCKER.md.
- src/configure's dependency-checker predates 64-bit multilib distros
  (only checked /usr/lib, never /usr/lib64) and was missing an ncur
  move-aside entry for the NCURSES-disabled build.

Added Dockerfile/.dockerignore/DOCKER.md documenting the build, the fixes,
and the one known-but-unfixed landmine (a SIGILL heap corruption in
sock::_close that reproduces on newer host GCC/glibc but not in the
container - latent, not fixed).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 17 insertions, 9 deletions

diff --git a/yhttpd/configure b/yhttpd/configure
index 9aab971..56f015f 100755
--- a/yhttpd/configure
+++ b/yhttpd/configure
@@ -51,17 +51,25 @@ perl -e '
  }
  &check_make;
  print "Checking compiler version\n";
- my $r = 0;
- for (my $i = 4; $i > 0 && $r == 0; --$i ) {
-    $r = &check_gcc(3,$i);
- }
- if ($r == 0) {
-  print "No suitable g++ compiler found!\n"; 
-  print "Please install a right version of GNU G++!\n";
+ # Accept any GNU g++ (the original check only accepted g++ 3.x; modern GCC
+ # works fine with the legacy-C++ fixes applied). Write g++.version as
+ # "<version>\ng++\n" - src/configure reads the last line as the compiler.
+ my $ver = `g++ -dumpversion 2>/dev/null`;
+ chomp $ver;
+ if ( $ver eq "" ) {
+  print "No GNU g++ compiler found!\nPlease install GNU G++!\n";
   exit(1);
  }
- 
- system("perl \"scripts/config.pl\"");
+ `echo $ver > g++.version`;
+ `echo g++ >> g++.version`;
+ print "GNU G++ $ver found!\n";
+
+ # -I. : scripts/config.pl does "use scripts::modules::file", which needs
+ # "." on @INC. Perl 5.26+ dropped "." from the default @INC, so this
+ # silently BEGIN-failed on modern Perl (the "yes" answer was never even
+ # read - it happened to be harmless only because the committed glob.h
+ # defaults were already correct).
+ system("perl -I. \"scripts/config.pl\"");
  chdir("src");
  system("./configure ".join(" ", @ARGV));
  chdir("..");