Merge bitcoin/bitcoin#28981: Replace Boost.Process with cpp-subprocess

d5a7155 build: remove boost::process dependency for building external signer support (Sebastian Falbesoner)
70434b1 external_signer: replace boost::process with cpp-subprocess (Sebastian Falbesoner)
cc8b987 Add `cpp-subprocess` header-only library (Hennadii Stepanov)

Pull request description:

  Closes bitcoin/bitcoin#24907.

  This PR is based on **theStack**'s [work](bitcoin/bitcoin#24907 (comment)).

  The `subprocess.hpp` header has been sourced from the [upstream repo](https://github.com/arun11299/cpp-subprocess) with the only modification being the removal of convenience functions, which are not utilized in our codebase.

  Windows-related changes will be addressed in subsequent follow-ups.

ACKs for top commit:
  achow101:
    reACK d5a7155
  Sjors:
    re-tACK d5a7155
  theStack:
    Light re-ACK d5a7155
  fanquake:
    ACK d5a7155 - with the expectation that this code is going to be maintained as our own. Next PRs should:

Tree-SHA512: d7fb6fecc3f5792496204190afb7d85b3e207b858fb1a75efe483c05260843b81b27d14b299323bb667c990e87a07197059afea3796cf218ed8b614086bd3611

Author: fanquake

configure.ac

@@ -307,9 +307,9 @@ AC_ARG_ENABLE([werror],
     [enable_werror=no])
 
 AC_ARG_ENABLE([external-signer],
-    [AS_HELP_STRING([--enable-external-signer],[compile external signer support (default is auto, requires Boost::Process)])],
+    [AS_HELP_STRING([--enable-external-signer],[compile external signer support (default is yes)])],
     [use_external_signer=$enableval],
-    [use_external_signer=auto])
+    [use_external_signer=yes])
 
 AC_LANG_PUSH([C++])
 
@@ -1414,56 +1414,14 @@ if test "$use_boost" = "yes"; then
   fi
 fi
 
-if test "$use_external_signer" != "no"; then
-  AC_MSG_CHECKING([whether Boost.Process can be used])
-  TEMP_CXXFLAGS="$CXXFLAGS"
-  dnl Boost 1.78 requires the following workaround.
-  dnl See: https://github.com/boostorg/process/issues/235
-  CXXFLAGS="$CXXFLAGS -Wno-error=narrowing"
-  TEMP_CPPFLAGS="$CPPFLAGS"
-  CPPFLAGS="$CPPFLAGS $BOOST_CPPFLAGS"
-  TEMP_LDFLAGS="$LDFLAGS"
-  dnl Boost 1.73 and older require the following workaround.
-  LDFLAGS="$LDFLAGS $PTHREAD_CFLAGS"
-  AC_LINK_IFELSE([AC_LANG_PROGRAM([[
-    #define BOOST_PROCESS_USE_STD_FS
-    #include <boost/process.hpp>
-  ]],[[
-    namespace bp = boost::process;
-    bp::opstream stdin_stream;
-    bp::ipstream stdout_stream;
-    bp::child c("dummy", bp::std_out > stdout_stream, bp::std_err > stdout_stream, bp::std_in < stdin_stream);
-    stdin_stream << std::string{"test"} << std::endl;
-    if (c.running()) c.terminate();
-    c.wait();
-    c.exit_code();
-  ]])],
-    [have_boost_process="yes"],
-    [have_boost_process="no"])
-  LDFLAGS="$TEMP_LDFLAGS"
-  CPPFLAGS="$TEMP_CPPFLAGS"
-  CXXFLAGS="$TEMP_CXXFLAGS"
-  AC_MSG_RESULT([$have_boost_process])
-  if test "$have_boost_process" = "yes"; then
-    case $host in
-      dnl Boost Process for Windows uses Boost ASIO. Boost ASIO performs
-      dnl pre-main init of Windows networking libraries, which we do not
-      dnl want.
-      *mingw*)
-        use_external_signer="no"
-      ;;
-      *)
-        use_external_signer="yes"
-        AC_DEFINE([ENABLE_EXTERNAL_SIGNER], [1], [Define if external signer support is enabled])
-        AC_DEFINE([BOOST_PROCESS_USE_STD_FS], [1], [Defined to avoid Boost::Process trying to use Boost Filesystem])
-      ;;
-    esac
-  else
-    if test "$use_external_signer" = "yes"; then
-      AC_MSG_ERROR([External signing is not supported for this Boost version])
-    fi
-    use_external_signer="no";
-  fi
+case $host in
+  dnl Re-enable it after enabling Windows support in cpp-subprocess.
+  *mingw*)
+    use_external_signer="no"
+  ;;
+esac
+if test "$use_external_signer" = "yes"; then
+  AC_DEFINE([ENABLE_EXTERNAL_SIGNER], [1], [Define if external signer support is enabled])
 fi
 AM_CONDITIONAL([ENABLE_EXTERNAL_SIGNER], [test "$use_external_signer" = "yes"])
 

src/Makefile.am

@@ -320,6 +320,7 @@ BITCOIN_CORE_H = \
   util/sock.h \
   util/spanparsing.h \
   util/string.h \
+  util/subprocess.hpp \
   util/syserror.h \
   util/task_runner.h \
   util/thread.h \

src/common/run_command.cpp

@@ -12,39 +12,34 @@
 #include <univalue.h>
 
 #ifdef ENABLE_EXTERNAL_SIGNER
-#include <boost/process.hpp>
+#include <util/subprocess.hpp>
 #endif // ENABLE_EXTERNAL_SIGNER
 
 UniValue RunCommandParseJSON(const std::string& str_command, const std::string& str_std_in)
 {
 #ifdef ENABLE_EXTERNAL_SIGNER
-    namespace bp = boost::process;
+    namespace sp = subprocess;
 
     UniValue result_json;
-    bp::opstream stdin_stream;
-    bp::ipstream stdout_stream;
-    bp::ipstream stderr_stream;
+    std::istringstream stdout_stream;
+    std::istringstream stderr_stream;
 
     if (str_command.empty()) return UniValue::VNULL;
 
-    bp::child c(
-        str_command,
-        bp::std_out > stdout_stream,
-        bp::std_err > stderr_stream,
-        bp::std_in < stdin_stream
-    );
+    auto c = sp::Popen(str_command, sp::input{sp::PIPE}, sp::output{sp::PIPE}, sp::error{sp::PIPE});
     if (!str_std_in.empty()) {
-        stdin_stream << str_std_in << std::endl;
+        c.send(str_std_in);
     }
-    stdin_stream.pipe().close();
+    auto [out_res, err_res] = c.communicate();
+    stdout_stream.str(std::string{out_res.buf.begin(), out_res.buf.end()});
+    stderr_stream.str(std::string{err_res.buf.begin(), err_res.buf.end()});
 
     std::string result;
     std::string error;
     std::getline(stdout_stream, result);
     std::getline(stderr_stream, error);
 
-    c.wait();
-    const int n_error = c.exit_code();
+    const int n_error = c.retcode();
     if (n_error) throw std::runtime_error(strprintf("RunCommandParseJSON error: process(%s) returned %d: %s\n", str_command, n_error, error));
     if (!result_json.read(result)) throw std::runtime_error("Unable to parse JSON: " + result);
 

src/external_signer.cpp

@@ -62,12 +62,12 @@ bool ExternalSigner::Enumerate(const std::string& command, std::vector<ExternalS
 
 UniValue ExternalSigner::DisplayAddress(const std::string& descriptor) const
 {
-    return RunCommandParseJSON(m_command + " --fingerprint \"" + m_fingerprint + "\"" + NetworkArg() + " displayaddress --desc \"" + descriptor + "\"");
+    return RunCommandParseJSON(m_command + " --fingerprint " + m_fingerprint + NetworkArg() + " displayaddress --desc " + descriptor);
 }
 
 UniValue ExternalSigner::GetDescriptors(const int account)
 {
-    return RunCommandParseJSON(m_command + " --fingerprint \"" + m_fingerprint + "\"" + NetworkArg() + " getdescriptors --account " + strprintf("%d", account));
+    return RunCommandParseJSON(m_command + " --fingerprint " + m_fingerprint + NetworkArg() + " getdescriptors --account " + strprintf("%d", account));
 }
 
 bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::string& error)
@@ -93,8 +93,8 @@ bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::str
         return false;
     }
 
-    const std::string command = m_command + " --stdin --fingerprint \"" + m_fingerprint + "\"" + NetworkArg();
-    const std::string stdinStr = "signtx \"" + EncodeBase64(ssTx.str()) + "\"";
+    const std::string command = m_command + " --stdin --fingerprint " + m_fingerprint + NetworkArg();
+    const std::string stdinStr = "signtx " + EncodeBase64(ssTx.str());
 
     const UniValue signer_result = RunCommandParseJSON(command, stdinStr);
 

src/test/system_tests.cpp

@@ -11,7 +11,7 @@
 #include <univalue.h>
 
 #ifdef ENABLE_EXTERNAL_SIGNER
-#include <boost/process.hpp>
+#include <util/subprocess.hpp>
 #endif // ENABLE_EXTERNAL_SIGNER
 
 #include <boost/test/unit_test.hpp>
@@ -34,20 +34,16 @@ BOOST_AUTO_TEST_CASE(run_command)
         BOOST_CHECK(result.isNull());
     }
     {
-        const UniValue result = RunCommandParseJSON("echo \"{\"success\": true}\"");
+        const UniValue result = RunCommandParseJSON("echo {\"success\": true}");
         BOOST_CHECK(result.isObject());
         const UniValue& success = result.find_value("success");
         BOOST_CHECK(!success.isNull());
         BOOST_CHECK_EQUAL(success.get_bool(), true);
     }
     {
-        // An invalid command is handled by Boost
-        const int expected_error{2};
-        BOOST_CHECK_EXCEPTION(RunCommandParseJSON("invalid_command"), boost::process::process_error, [&](const boost::process::process_error& e) {
-            BOOST_CHECK(std::string(e.what()).find("RunCommandParseJSON error:") == std::string::npos);
-            BOOST_CHECK_EQUAL(e.code().value(), expected_error);
-            return true;
-        });
+        // An invalid command is handled by cpp-subprocess
+        const std::string expected{"execve failed: "};
+        BOOST_CHECK_EXCEPTION(RunCommandParseJSON("invalid_command"), subprocess::CalledProcessError, HasReason(expected));
     }
     {
         // Return non-zero exit code, no output to stderr