diff --git a/.cirrus.yml b/.cirrus.yml
index a09ed95051..fde5147ea7 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -39,6 +39,7 @@ freebsd_task:
     "CXX_PATH=`which ${CXX}`",
     "cd test",
     "echo \"using ${TEST_TOOLSET} : : ${CXX_PATH} ;\" > ${HOME}/user-config.jam",
+    "python3 grep.py ${TEST_TOOLSET}",
     "python3 test_all.py ${TEST_TOOLSET}",
     "cd ..",
   ]
diff --git a/README.adoc b/README.adoc
index 5bc9056a95..63722c83fa 100644
--- a/README.adoc
+++ b/README.adoc
@@ -20,7 +20,7 @@ Continuously tested on:
 * Linux GCC 9, 10, 11, 12
 * macOS Xcode 11.7, 12.4, 12.5.1, 13.4.1, 14.0.1, 14.1, 14.2
 * Windows MinGW 8.1.0
-* Windows VS 2013, 2015, 2017, 2019, 2022
+* Windows 2015, 2017, 2019, 2022
 * Cygwin 3.1.7 x64
 * Ubuntu 20.04 GCC 9 (armhf, arm64, ppc64el)
 * Debian 11 GCC 10 (armhf)
diff --git a/appveyor.yml b/appveyor.yml
index 6b8233e978..933ab88fd9 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -2,7 +2,7 @@
 # subject to the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 #
-# Copyright Rene Ferdinand Rivera Morell 2015-2020.
+# Copyright Rene Ferdinand Rivera Morell 2015-2023.
 
 branches:
   only:
@@ -11,6 +11,15 @@ branches:
     - /feature\/.*/
     - /backport-.*/
 
+skip_commits:
+  files:
+    - ".circleci/*"
+    - ".cirrus.yml"
+    - ".drone.star"
+    - ".github/workflows/*"
+    - ".semaphore/*"
+    - "azure-pipelines.yml"
+
 environment:
   matrix:
   - job_name: 'Visual Studio 2017, Test'
@@ -23,11 +32,6 @@ environment:
     TOOLSET: vc14
     TEST_TOOLSET: msvc-14.0
     APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-  - job_name: 'Visual Studio 2013, Test'
-    job_group: 'Test'
-    TOOLSET: vc12
-    TEST_TOOLSET: msvc-12.0
-    APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
   - job_name: 'Clang 9 (VS2015), Test'
     job_group: 'Test'
     TOOLSET: clang-win
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 8c08d02519..4b0f9178f6 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -99,6 +99,7 @@ stages:
         Clang ${{variables.clang_latest}} (VS${{variables.vs_latest}}): {TOOLSET: clang-win, TEST_TOOLSET: clang-win, VM_IMAGE: "${{variables.windows_latest_vm}}"}
     pool:
       vmImage: $(VM_IMAGE)
+    continueOnError: 'true'
     steps:
     - template: .ci/azp-windows-test.yml
 
diff --git a/src/engine/builtins.cpp b/src/engine/builtins.cpp
index df03162bc0..ec90962014 100644
--- a/src/engine/builtins.cpp
+++ b/src/engine/builtins.cpp
@@ -491,7 +491,6 @@ LIST * builtin_calc( FRAME * frame, int flags )
     long lhs_value;
     long rhs_value;
     long result_value;
-    char buffer[ 16 ];
     char const * lhs;
     char const * op;
     char const * rhs;
@@ -519,8 +518,7 @@ LIST * builtin_calc( FRAME * frame, int flags )
     else
         return L0;
 
-    sprintf( buffer, "%ld", result_value );
-    result = list_push_back( result, object_new( buffer ) );
+    result = list_push_back( result, b2::value::as_string(result_value) );
     return result;
 }
 
@@ -1408,10 +1406,8 @@ LIST * builtin_backtrace( FRAME * frame, int flags )
     {
         char const * file;
         int line;
-        char buf[ 32 ];
         string module_name[ 1 ];
         get_source_line( frame, &file, &line );
-        sprintf( buf, "%d", line );
         string_new( module_name );
         if ( frame->module->name )
         {
@@ -1419,7 +1415,7 @@ LIST * builtin_backtrace( FRAME * frame, int flags )
             string_append( module_name, "." );
         }
         result = list_push_back( result, object_new( file ) );
-        result = list_push_back( result, object_new( buf ) );
+        result = list_push_back( result, b2::value::as_string(line) );
         result = list_push_back( result, object_new( module_name->value ) );
         result = list_push_back( result, object_new( frame->rulename ) );
         string_free( module_name );
@@ -1695,12 +1691,10 @@ LIST * builtin_nearest_user_location( FRAME * frame, int flags )
         LIST * result = L0;
         char const * file;
         int line;
-        char buf[ 32 ];
 
         get_source_line( nearest_user_frame, &file, &line );
-        sprintf( buf, "%d", line );
         result = list_push_back( result, object_new( file ) );
-        result = list_push_back( result, object_new( buf ) );
+        result = list_push_back( result, b2::value::as_string(line) );
         return result;
     }
 }
@@ -1730,8 +1724,13 @@ LIST * builtin_md5( FRAME * frame, int flags )
     md5_append( &state, (md5_byte_t const *)s, strlen( s ) );
     md5_finish( &state, digest );
 
+    static const char hex_digit[] = "0123456789abcdef";
     for ( di = 0; di < 16; ++di )
-        sprintf( hex_output + di * 2, "%02x", digest[ di ] );
+    {
+        hex_output[di*2+0] = hex_digit[digest[di]>>4];
+        hex_output[di*2+1] = hex_digit[digest[di]&0xF];
+    }
+    hex_output[16*2] = '\0';
 
     return list_new( object_new( hex_output ) );
 }
@@ -1742,7 +1741,6 @@ LIST * builtin_file_open( FRAME * frame, int flags )
     char const * name = object_str( list_front( lol_get( frame->args, 0 ) ) );
     char const * mode = object_str( list_front( lol_get( frame->args, 1 ) ) );
     int fd;
-    char buffer[ sizeof( "4294967295" ) ];
 
     if ( strcmp(mode, "t") == 0 )
     {
@@ -1772,8 +1770,7 @@ LIST * builtin_file_open( FRAME * frame, int flags )
 
     if ( fd != -1 )
     {
-        sprintf( buffer, "%d", fd );
-        return list_new( object_new( buffer ) );
+        return list_new( b2::value::as_string(fd) );
     }
     return L0;
 }
@@ -2114,8 +2111,7 @@ LIST * builtin_shell( FRAME * frame, int flags )
         /* Harmonize VMS success status with POSIX */
         if ( exit_status == 1 ) exit_status = EXIT_SUCCESS;
 #endif
-        sprintf( buffer, "%d", exit_status );
-        result = list_push_back( result, object_new( buffer ) );
+        result = list_push_back( result, b2::value::as_string(exit_status) );
     }
 
     return result;
diff --git a/src/engine/config.h b/src/engine/config.h
index 99e153ec05..a732d7349a 100644
--- a/src/engine/config.h
+++ b/src/engine/config.h
@@ -2,7 +2,7 @@
 #define B2_CONFIG_H
 
 /*
-Copyright 2002-2021 Rene Rivera.
+Copyright 2002-2023 Rene Rivera.
 Distributed under the Boost Software License, Version 1.0.
 (See accompanying file LICENSE.txt or copy at
 https://www.bfgroup.xyz/b2/LICENSE.txt)
@@ -42,38 +42,13 @@ Distributed under the Boost Software License, Version 1.0.
 #define _FILE_OFFSET_BITS 64
 #endif
 
-// Correct missing types in some earlier compilers..
-
-#include <stdint.h>
-#ifndef INT32_MIN
-
-// VS 2013 is barely C++11/C99. And opts to not provide specific sized int
-// types. Provide a generic implementation of the sizes we use.
-#if UINT_MAX == 0xffffffff
-typedef int int32_t;
-#elif (USHRT_MAX == 0xffffffff)
-typedef short int32_t;
-#elif ULONG_MAX == 0xffffffff
-typedef long int32_t;
-#endif
-
-#endif
-
 // Account for incomplete C++ standard implementations.
 
-// VS 2012 doesn't implement noexcept.
-#if defined(_MSC_VER) && (_MSC_VER < 1900)
-#define B2_NOEXCEPT
-#endif
-
 #ifndef B2_NOEXCEPT
 #define B2_NOEXCEPT noexcept
 #endif
 
 // Indicate if we can use std::thread and friends.
-#if defined(_MSC_VER) && _MSC_VER <= 1800
-#define B2_USE_STD_THREADS 0
-#endif
 #ifndef B2_USE_STD_THREADS
 #define B2_USE_STD_THREADS 1
 #endif
diff --git a/src/engine/debugger.cpp b/src/engine/debugger.cpp
index c9b87cf267..5b10bb4f26 100644
--- a/src/engine/debugger.cpp
+++ b/src/engine/debugger.cpp
@@ -1108,7 +1108,6 @@ static void debug_parent_copy_breakpoints( void )
 static void debug_start_child( int argc, const char * * argv )
 {
 #if NT
-    char buf[ 80 ];
     HANDLE pipe1[ 2 ];
     HANDLE pipe2[ 2 ];
     string self[ 1 ];
@@ -1143,12 +1142,10 @@ static void debug_start_child( int argc, const char * * argv )
     string_copy( command_line, "b2 " );
     /* Pass the handles as the first and second arguments. */
     string_append( command_line, debugger_opt );
-    sprintf( buf, "%p", pipe1[ 0 ] );
-    string_append( command_line, buf );
+    string_append( command_line, b2::value::format( "%p", pipe1[ 0 ] )->str() );
     string_push_back( command_line, ' ' );
     string_append( command_line, debugger_opt );
-    sprintf( buf, "%p", pipe2[ 1 ] );
-    string_append( command_line, buf );
+    string_append( command_line, b2::value::format( "%p", pipe2[ 1 ] )->str() );
     /* Pass the rest of the command line. */
 	{
         int i;
@@ -1495,7 +1492,6 @@ static void debug_parent_delete( int argc, const char * * argv )
 
 static void debug_parent_clear( int argc, const char * * argv )
 {
-    char buf[ 16 ];
     const char * new_args[ 2 ];
     int id;
     if ( argc < 2 )
@@ -1520,9 +1516,9 @@ static void debug_parent_clear( int argc, const char * * argv )
         printf( "Deleted breakpoint %d\n", id );
     }
 
-    sprintf( buf, "%d", id );
+    auto id_s = std::to_string(id);
     new_args[ 0 ] = "delete";
-    new_args[ 1 ] = buf;
+    new_args[ 1 ] = id_s.c_str();
     debug_parent_delete( 2, new_args );
 }
 
@@ -1577,9 +1573,8 @@ static void debug_parent_backtrace( int argc, const char * * argv )
     for ( i = 0; i < depth; ++i )
     {
         FRAME_INFO frame;
-        char buf[ 16 ];
-        sprintf( buf, "%d", i );
-        new_args[ 2 ] = buf;
+        auto i_s = std::to_string(i);
+        new_args[ 2 ] = i_s.c_str();
         debug_parent_forward_nowait( 3, new_args, 0, 0 );
         debug_frame_read( command_child, &frame );
         printf( "#%d  in ", i );
@@ -1937,10 +1932,9 @@ static void debug_mi_break_insert( int argc, const char * * argv )
 
     if ( disabled )
     {
-        char buf[ 80 ];
-        sprintf( buf, "%d", num_breakpoints );
+        auto num_breakpoints_s = std::to_string(num_breakpoints);
         inner_argv[ 0 ] = "disable";
-        inner_argv[ 1 ] = buf;
+        inner_argv[ 1 ] = num_breakpoints_s.c_str();
         debug_child_disable( 2, inner_argv );
         debug_parent_forward_nowait( 2, inner_argv, 1, 0 );
     }
diff --git a/src/engine/execcmd.cpp b/src/engine/execcmd.cpp
index dfbd5a7f8a..c25416f3da 100644
--- a/src/engine/execcmd.cpp
+++ b/src/engine/execcmd.cpp
@@ -43,8 +43,6 @@ static int intr;
 void argv_from_shell( char const * * argv, LIST * shell, char const * command,
     int32_t const slot )
 {
-    static char jobno[ 12 ];
-
     int i;
     int gotpercent = 0;
     LISTITER iter = list_begin( shell );
@@ -52,14 +50,14 @@ void argv_from_shell( char const * * argv, LIST * shell, char const * command,
 
     assert( 0 <= slot );
     assert( slot < 999 );
-    sprintf( jobno, "%d", slot + 1 );
+    auto jobno = b2::value::as_string( slot + 1 );
 
     for ( i = 0; iter != end && i < MAXARGC; ++i, iter = list_next( iter ) )
     {
         switch ( object_str( list_item( iter ) )[ 0 ] )
         {
             case '%': argv[ i ] = command; ++gotpercent; break;
-            case '!': argv[ i ] = jobno; break;
+            case '!': argv[ i ] = jobno->str(); break;
             default : argv[ i ] = object_str( list_item( iter ) );
         }
     }
diff --git a/src/engine/execnt.cpp b/src/engine/execnt.cpp
index 1cf627f2fc..28c3a86078 100644
--- a/src/engine/execnt.cpp
+++ b/src/engine/execnt.cpp
@@ -1219,9 +1219,8 @@ static FILE * open_command_file( int32_t const slot )
         DWORD const procID = GetCurrentProcessId();
         string const * const tmpdir = path_tmpdir();
         string_new( command_file );
-        string_reserve( command_file, tmpdir->size + 64 );
-        command_file->size = sprintf( command_file->value,
-            "%s\\jam%lu-%02d-##.bat", tmpdir->value, procID, slot );
+        string_copy( command_file, b2::value::format( "%s\\jam%lu-%02d-##.bat",
+            tmpdir->value, procID, slot )->str() );
     }
 
     /* For some reason opening a command file can fail intermittently. But doing
@@ -1321,7 +1320,6 @@ static void string_new_from_argv( string * result, char const * const * argv )
 static void reportWindowsError( char const * const apiName, int32_t slot )
 {
     char * errorMessage;
-    char buf[24];
     string * err_buf;
     timing_info time;
     DWORD const errorCode = GetLastError();
@@ -1343,8 +1341,8 @@ static void reportWindowsError( char const * const apiName, int32_t slot )
         err_buf = cmdtab[ slot ].buffer_out;
     string_append( err_buf, apiName );
     string_append( err_buf, "() Windows API failed: " );
-    sprintf( buf, "%lu", errorCode );
-    string_append( err_buf, buf );
+    auto errorCode_s = std::to_string( errorCode );
+    string_append( err_buf, errorCode_s.c_str() );
 
     if ( !apiResult )
         string_append( err_buf, ".\n" );
diff --git a/src/engine/filent.cpp b/src/engine/filent.cpp
index faf4833554..cfe369e010 100644
--- a/src/engine/filent.cpp
+++ b/src/engine/filent.cpp
@@ -367,7 +367,6 @@ void file_archscan( char const * arch, scanback func, void * closure )
     {
         FILELISTITER iter = filelist_begin( archive->members );
         FILELISTITER const end = filelist_end( archive->members );
-        char buf[ MAXJPATH ];
 
         for ( ; iter != end ; iter = filelist_next( iter ) )
         {
@@ -375,11 +374,10 @@ void file_archscan( char const * arch, scanback func, void * closure )
 
             /* Construct member path: 'archive-path(member-name)'
              */
-            sprintf( buf, "%s(%s)",
-                object_str( archive->file->name ),
-                object_str( member_file->name ) );
             {
-                OBJECT * member = object_new( buf );
+                OBJECT * member = b2::value::format( "%s(%s)",
+                    object_str( archive->file->name ),
+                    object_str( member_file->name ) );
                 (*func)( closure, member, 1 /* time valid */, &member_file->time );
                 object_free( member );
             }
@@ -486,9 +484,9 @@ int file_collect_archive_content_( file_archive_info_t * const archive )
                 name = c + 1;
         }
 
-        sprintf( buf, "%.*s", int(endname - name), name );
+        auto member_name = b2::value::format( "%.*s", int(endname - name), name );
 
-        if ( strcmp( buf, "") != 0 )
+        if ( member_name->as_string().size > 0 )
         {
             file_info_t * member = 0;
 
@@ -497,7 +495,7 @@ int file_collect_archive_content_( file_archive_info_t * const archive )
              * Here we reverse the stored sequence by pushing members to front of
              * member file list to get the intended members order.
              */
-            archive->members = filelist_push_front( archive->members, object_new( buf ) );
+            archive->members = filelist_push_front( archive->members, member_name );
             member = filelist_front( archive->members );
             member->is_file = 1;
             member->is_dir = 0;
diff --git a/src/engine/filesys.cpp b/src/engine/filesys.cpp
index d6728e0a93..98e1aabe87 100644
--- a/src/engine/filesys.cpp
+++ b/src/engine/filesys.cpp
@@ -397,7 +397,6 @@ static void file_archivescan_impl( OBJECT * path, archive_scanback func, void *
     {
         FILELISTITER iter = filelist_begin( archive->members );
         FILELISTITER const end = filelist_end( archive->members );
-        char buf[ MAXJPATH ];
 
         for ( ; iter != end ; iter = filelist_next( iter ) )
         {
@@ -406,12 +405,10 @@ static void file_archivescan_impl( OBJECT * path, archive_scanback func, void *
 
             /* Construct member path: 'archive-path(member-name)'
              */
-            sprintf( buf, "%s(%s)",
-                object_str( archive->file->name ),
-                object_str( member_file->name ) );
-
             {
-                OBJECT * member = object_new( buf );
+                OBJECT * member = b2::value::format( "%s(%s)",
+                    object_str( archive->file->name ),
+                    object_str( member_file->name ) );
                 (*func)( closure, member, symbols, 1, &member_file->time );
                 object_free( member );
             }
diff --git a/src/engine/fileunix.cpp b/src/engine/fileunix.cpp
index 6cde3f695f..3a7907eadb 100644
--- a/src/engine/fileunix.cpp
+++ b/src/engine/fileunix.cpp
@@ -229,7 +229,6 @@ void file_archscan( char const * arch, scanback func, void * closure )
     {
         FILELISTITER iter = filelist_begin( archive->members );
         FILELISTITER const end = filelist_end( archive->members );
-        char buf[ MAXJPATH ];
 
         for ( ; iter != end ; iter = filelist_next( iter ) )
         {
@@ -237,11 +236,10 @@ void file_archscan( char const * arch, scanback func, void * closure )
 
             /* Construct member path: 'archive-path(member-name)'
              */
-            sprintf( buf, "%s(%s)",
-                object_str( archive->file->name ),
-                object_str( member_file->name ) );
             {
-                OBJECT * member = object_new( buf );
+                OBJECT * member = b2::value::format( "%s(%s)",
+                    object_str( archive->file->name ),
+                    object_str( member_file->name ) );
                 (*func)( closure, member, 1 /* time valid */, &member_file->time );
                 object_free( member );
             }
@@ -354,13 +352,13 @@ int file_collect_archive_content_( file_archive_info_t * const archive )
         if ( DEBUG_BINDSCAN )
             out_printf( "archive name %s found\n", lar_name );
 
-        sprintf( buf, "%s", lar_name );
+        auto name = b2::value::format( "%s", lar_name );
 
-        if ( strcmp( buf, "") != 0 )
+        if ( name->as_string().size > 0 )
         {
             file_info_t * member = 0;
 
-            archive->members = filelist_push_back( archive->members, object_new( buf ) );
+            archive->members = filelist_push_back( archive->members, name);
             member = filelist_back( archive->members );
             member->is_file = 1;
             member->is_dir = 0;
@@ -419,13 +417,13 @@ static void collect_archive_content_small( int fd, file_archive_info_t * const a
 
         ar_hdr.hdr._ar_name.ar_name[ lar_namlen ] = '\0';
 
-        sprintf( buf, "%s", ar_hdr.hdr._ar_name.ar_name );
+        auto name = b2::value::format( "%s", ar_hdr.hdr._ar_name.ar_name );
 
-        if ( strcmp( buf, "") != 0 )
+        if ( name->as_string().size > 0 )
         {
             file_info_t * member = 0;
 
-            archive->members = filelist_push_back( archive->members, object_new( buf ) );
+            archive->members = filelist_push_back( archive->members, name );
             member = filelist_back( archive->members );
             member->is_file = 1;
             member->is_dir = 0;
@@ -474,13 +472,13 @@ static void collect_archive_content_big( int fd, file_archive_info_t * const arc
 
         ar_hdr.hdr._ar_name.ar_name[ lar_namlen ] = '\0';
 
-        sprintf( buf, "%s", ar_hdr.hdr._ar_name.ar_name );
+        auto name = b2::value::format( "%s", ar_hdr.hdr._ar_name.ar_name );
 
-        if ( strcmp( buf, "") != 0 )
+        if ( name->as_string().size > 0 )
         {
             file_info_t * member = 0;
 
-            archive->members = filelist_push_back( archive->members, object_new( buf ) );
+            archive->members = filelist_push_back( archive->members, name );
             member = filelist_back( archive->members );
             member->is_file = 1;
             member->is_dir = 0;
diff --git a/src/engine/filevms.cpp b/src/engine/filevms.cpp
index cf24b8c602..b3b2303e73 100644
--- a/src/engine/filevms.cpp
+++ b/src/engine/filevms.cpp
@@ -20,6 +20,9 @@
 #include "pathsys.h"
 #include "jam_strings.h"
 
+#include <algorithm>
+#include <cctype>
+
 
 #ifdef OS_VMS
 
@@ -310,9 +313,12 @@ static unsigned int set_archive_member( struct dsc$descriptor_s *module,
         file_info_t * member = 0;
 
         /* Construct member's filename as lowercase "module.obj" */
-        sprintf( buf, "%s.obj", filename );
-        downcase_inplace( buf );
-        archive->members = filelist_push_back( archive->members, object_new( buf ) );
+        std::string name = filename;
+        name += ".obj";
+        std::transform(name.begin(), name.end(), name.begin(),
+            [](unsigned char c) { return std::tolower(c); });
+        archive->members = filelist_push_back( archive->members,
+            b2::value::make( name ) );
 
         member = filelist_back( archive->members );
         member->is_file = 1;
@@ -350,7 +356,6 @@ void file_archscan( char const * arch, scanback func, void * closure )
     {
         FILELISTITER iter = filelist_begin( archive->members );
         FILELISTITER const end = filelist_end( archive->members );
-        char buf[ MAXJPATH ];
 
         for ( ; iter != end ; iter = filelist_next( iter ) )
         {
@@ -359,11 +364,10 @@ void file_archscan( char const * arch, scanback func, void * closure )
 
             /* Construct member path: 'archive-path(member-name)'
              */
-            sprintf( buf, "%s(%s)",
-                object_str( archive->file->name ),
-                object_str( member_file->name ) );
             {
-                OBJECT * member = object_new( buf );
+                OBJECT * member = b2::value::format( "%s(%s)",
+                    object_str( archive->file->name ),
+                    object_str( member_file->name ) );
                 (*func)( closure, member, 1 /* time valid */, &member_file->time );
                 object_free( member );
             }
diff --git a/src/engine/hcache.cpp b/src/engine/hcache.cpp
index f606a65fa2..02b8d8c141 100644
--- a/src/engine/hcache.cpp
+++ b/src/engine/hcache.cpp
@@ -171,11 +171,14 @@ OBJECT * read_netstring( FILE * f )
  * Write a netstring.
  */
 
-void write_netstring( FILE * f, char const * s )
+template <typename... Args>
+void write_netstring( FILE * f, char const * format, Args... args )
 {
-    if ( !s )
-        s = "";
-    fprintf( f, "%lu\t%s\n", (long unsigned)strlen( s ), s );
+    if ( format == nullptr ) format = "";
+    auto size = std::snprintf(nullptr, 0, format, args...);
+    std::unique_ptr<char[]> s(new char[size+1]);
+    std::snprintf(s.get(), size+1, format, args...);
+    fprintf( f, "%lu\t%s\n", (long unsigned)size, s.get() );
 }
 
 
@@ -373,49 +376,38 @@ void hcache_done()
     maxage = cache_maxage();
 
     /* Print out the version. */
-    write_netstring( f, CACHE_FILE_VERSION );
+    write_netstring( f, "%s",CACHE_FILE_VERSION );
 
     c = hcachelist;
     for ( c = hcachelist; c; c = c->next )
     {
         LISTITER iter;
         LISTITER end;
-        char time_secs_str[ 30 ];
-        char time_nsecs_str[ 30 ];
-        char age_str[ 30 ];
-        char includes_count_str[ 30 ];
-        char hdrscan_count_str[ 30 ];
 
         if ( maxage == 0 )
             c->age = 0;
         else if ( c->age > maxage )
             continue;
 
-        sprintf( includes_count_str, "%lu", (long unsigned)list_length(
+        write_netstring( f, "%s", CACHE_RECORD_HEADER );
+        write_netstring( f, "%s", object_str( c->boundname ) );
+        write_netstring( f, "%lu", (long unsigned)c->time.secs );
+        write_netstring( f, "%lu", (long unsigned)c->time.nsecs );
+        write_netstring( f, "%lu", (long unsigned)c->age );
+        write_netstring( f, "%lu", (long unsigned)list_length(
             c->includes ) );
-        sprintf( hdrscan_count_str, "%lu", (long unsigned)list_length(
-            c->hdrscan ) );
-        sprintf( time_secs_str, "%lu", (long unsigned)c->time.secs );
-        sprintf( time_nsecs_str, "%lu", (long unsigned)c->time.nsecs );
-        sprintf( age_str, "%lu", (long unsigned)c->age );
-
-        write_netstring( f, CACHE_RECORD_HEADER );
-        write_netstring( f, object_str( c->boundname ) );
-        write_netstring( f, time_secs_str );
-        write_netstring( f, time_nsecs_str );
-        write_netstring( f, age_str );
-        write_netstring( f, includes_count_str );
         for ( iter = list_begin( c->includes ), end = list_end( c->includes );
             iter != end; iter = list_next( iter ) )
-            write_netstring( f, object_str( list_item( iter ) ) );
-        write_netstring( f, hdrscan_count_str );
+            write_netstring( f, "%s", object_str( list_item( iter ) ) );
+        write_netstring( f, "%lu", (long unsigned)list_length(
+            c->hdrscan ) );
         for ( iter = list_begin( c->hdrscan ), end = list_end( c->hdrscan );
             iter != end; iter = list_next( iter ) )
-            write_netstring( f, object_str( list_item( iter ) ) );
+            write_netstring( f, "%s", object_str( list_item( iter ) ) );
         fputs( "\n", f );
         ++header_count;
     }
-    write_netstring( f, CACHE_RECORD_END );
+    write_netstring( f, "%s", CACHE_RECORD_END );
 
     if ( DEBUG_HEADER )
         out_printf( "hcache written to %s.   %d dependencies, %.0f%% hit rate\n",
diff --git a/src/engine/make.cpp b/src/engine/make.cpp
index 5d37640350..90fbc17833 100644
--- a/src/engine/make.cpp
+++ b/src/engine/make.cpp
@@ -770,11 +770,9 @@ void make0
 
 static char const * target_name( TARGET * t )
 {
-    static char buf[ 1000 ];
     if ( t->flags & T_FLAG_INTERNAL )
     {
-        sprintf( buf, "%s (internal node)", object_str( t->name ) );
-        return buf;
+        return b2::value::format( "%s (internal node)", t->name->str() )->str();
     }
     return object_str( t->name );
 }
diff --git a/src/engine/output.cpp b/src/engine/output.cpp
index 196082c781..d4ab5c5a80 100644
--- a/src/engine/output.cpp
+++ b/src/engine/output.cpp
@@ -172,17 +172,13 @@ void errno_printf(char const * const f, ...)
 
 OBJECT * outf_int( int const value )
 {
-    char buffer[ 50 ];
-    sprintf( buffer, "%i", value );
-    return object_new( buffer );
+    return b2::value::as_string( value );
 }
 
 
 OBJECT * outf_double( double const value )
 {
-    char buffer[ 50 ];
-    sprintf( buffer, "%f", value );
-    return object_new( buffer );
+    return b2::value::as_string( value );
 }
 
 
diff --git a/src/engine/pathsys.cpp b/src/engine/pathsys.cpp
index 98606aff6c..22e8e81747 100644
--- a/src/engine/pathsys.cpp
+++ b/src/engine/pathsys.cpp
@@ -262,13 +262,11 @@ string const * path_tmpdir()
 
 OBJECT * path_tmpnam( void )
 {
-    char name_buffer[ 64 ];
     unsigned long const pid = path_get_process_id_();
-    static unsigned long t;
+    static unsigned long t = 0;
     if ( !t ) t = time( 0 ) & 0xffff;
     t += 1;
-    sprintf( name_buffer, "jam%lx%lx.000", pid, t );
-    return object_new( name_buffer );
+    return b2::value::format( "jam%lx%lx.000", pid, t );
 }
 
 
diff --git a/src/engine/scan.cpp b/src/engine/scan.cpp
index fcfd018b57..c7f2b16e3a 100644
--- a/src/engine/scan.cpp
+++ b/src/engine/scan.cpp
@@ -47,7 +47,7 @@ static int scanmode = SCAN_NORMAL;
 static int anyerrors = 0;
 
 
-static char * symdump( YYSTYPE * );
+static std::string symdump( YYSTYPE * );
 
 #define BIGGEST_TOKEN 10240  /* no single token can be larger */
 
@@ -77,7 +77,7 @@ void yyerror( char const * s )
      * hold the information about where reading it broke.
      */
     out_printf( "%s:%d: %s at %s\n", object_str( yylval.file ), yylval.line, s,
-            symdump( &yylval ) );
+            symdump( &yylval ).c_str() );
     ++anyerrors;
 }
 
@@ -239,7 +239,7 @@ static int use_new_scanner = 0;
 void do_token_warning()
 {
     out_printf( "%s:%d: %s %s\n", object_str( yylval.file ), yylval.line, "Unescaped special character in",
-            symdump( &yylval ) );
+            symdump( &yylval ).c_str() );
 }
 
 #define token_warning() has_token_warning = 1
@@ -764,7 +764,7 @@ int yylex()
     }
 
     if ( DEBUG_SCAN )
-        out_printf( "scan %s\n", symdump( &yylval ) );
+        out_printf( "scan %s\n", symdump( &yylval ).c_str() );
 
     return yylval.type;
 
@@ -777,18 +777,17 @@ int yylex()
 }
 
 
-static char * symdump( YYSTYPE * s )
+static std::string symdump( YYSTYPE * s )
 {
-    static char buf[ BIGGEST_TOKEN + 20 ];
     switch ( s->type )
     {
-        case EOF   : sprintf( buf, "EOF"                                        ); break;
-        case 0     : sprintf( buf, "unknown symbol %s", object_str( s->string ) ); break;
-        case ARG   : sprintf( buf, "argument %s"      , object_str( s->string ) ); break;
-        case STRING: sprintf( buf, "string \"%s\""    , object_str( s->string ) ); break;
-        default    : sprintf( buf, "keyword %s"       , s->keyword              ); break;
+        case EOF   : return "EOF"; break;
+        case 0     : return std::string("unknown symbol ") + s->string->str(); break;
+        case ARG   : return std::string("argument ") + s->string->str(); break;
+        case STRING: return std::string("string \"") + s->string->str() + "\""; break;
+        default    : return std::string("keyword ") + s->keyword; break;
     }
-    return buf;
+    return "";
 }
 
 
diff --git a/src/engine/tasks.cpp b/src/engine/tasks.cpp
index fb85d1b6e8..10e114592f 100644
--- a/src/engine/tasks.cpp
+++ b/src/engine/tasks.cpp
@@ -39,32 +39,32 @@ struct sync
 
 inline sync::sync()
 {
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	wait_arrived = false;
 	signal_arrived = false;
-	#endif
+#endif
 }
 
 inline void sync::wait()
 {
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	// Indicate that we waiting.
 	wait_arrived = true;
 	// Wait for the signal that we can proceed.
 	std::unique_lock<std::mutex> lock(arrived_mx);
 	arrived_cv.wait(lock, [this]() { return signal_arrived.load(); });
-	#endif
+#endif
 }
 
 inline bool sync::signal()
 {
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	// Wait for wait() to get called.
 	if (!wait_arrived.load()) return false;
 	// Tell the waiter that we arrived.
 	signal_arrived = true;
 	arrived_cv.notify_one();
-	#endif
+#endif
 	return true;
 }
 
@@ -218,14 +218,14 @@ inline executor::implementation::implementation(unsigned parallelism)
 	if (parallelism == 0) return;
 	// Launch the threads to cover the expected parallelism.
 	scope_lock_t lock(mx);
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	runners.reserve(parallelism);
 	for (; parallelism > 0; --parallelism)
 	{
 		running_count += 1;
 		runners.emplace_back([this]() { runner(); });
 	}
-	#endif
+#endif
 }
 
 inline void executor::implementation::push_group(std::shared_ptr<group> g)
@@ -236,16 +236,16 @@ inline void executor::implementation::push_group(std::shared_ptr<group> g)
 
 inline void executor::implementation::call_signal()
 {
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	call_cv.notify_one();
-	#endif
+#endif
 }
 
 inline std::function<void()> executor::implementation::call_get()
 {
 	std::function<void()> result;
 	scope_lock_t lock(mx);
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	// We only dequeue task calls when we have a thread to run them.
 	if (call_count < runners.size())
 	{
@@ -261,7 +261,7 @@ inline std::function<void()> executor::implementation::call_get()
 	}
 	// We don't have tasks to run, wait for some to become available.
 	call_cv.wait(lock);
-	#endif
+#endif
 	return result;
 }
 
@@ -279,7 +279,7 @@ inline bool executor::implementation::is_running()
 
 inline void executor::implementation::stop()
 {
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	// Stop all the runner threads (i.e. signal and wait).
 	std::vector<std::thread> to_join;
 	{
@@ -292,7 +292,7 @@ inline void executor::implementation::stop()
 		call_cv.notify_all();
 		t.join();
 	}
-	#endif
+#endif
 }
 
 void executor::implementation::runner()
@@ -316,13 +316,13 @@ void executor::implementation::runner()
 namespace {
 unsigned get_parallelism(int parallelism)
 {
-	#if B2_USE_STD_THREADS
+#if B2_USE_STD_THREADS
 	return parallelism >= 0
 		? parallelism
 		: std::min(unsigned(globs.jobs), system_info().cpu_thread_count()) - 1;
-	#else
+#else
 	return 0;
-	#endif
+#endif
 }
 } // namespace
 
diff --git a/src/engine/timestamp.cpp b/src/engine/timestamp.cpp
index 1664c64b57..9082f02dce 100644
--- a/src/engine/timestamp.cpp
+++ b/src/engine/timestamp.cpp
@@ -7,6 +7,7 @@
 /* This file is ALSO:
  * Copyright 2001-2004 David Abrahams.
  * Copyright 2020 Nikita Kniazev.
+ * Copyright 2023 René Ferdinand Rivera Morell.
  * Distributed under the Boost Software License, Version 1.0.
  * (See accompanying file LICENSE.txt or
  * https://www.bfgroup.xyz/b2/LICENSE.txt)
@@ -24,14 +25,15 @@
  */
 
 #include "jam.h"
-#include "timestamp.h"
 
 #include "filesys.h"
 #include "hash.h"
-#include "object.h"
-#include "pathsys.h"
 #include "jam_strings.h"
+#include "object.h"
 #include "output.h"
+#include "pathsys.h"
+#include "timestamp.h"
+#include "types.h"
 
 
 /*
@@ -182,12 +184,14 @@ void timestamp_max( timestamp * const max, timestamp const * const lhs,
 static char const * timestamp_formatstr( timestamp const * const time,
     char const * const format )
 {
+    // gmtime is not thread safe. And there's no alternative in C++11.
+    // So we make this whole thing exclusive to prevent errors.
+    static b2::mutex_t m;
+    b2::scope_lock_t l(m);
     static char result1[ 500 ];
-    static char result2[ 500 ];
     strftime( result1, sizeof( result1 ) / sizeof( *result1 ), format, gmtime(
         &time->secs ) );
-    sprintf( result2, result1, time->nsecs );
-    return result2;
+    return b2::value::format( result1, time->nsecs )->str();
 }
 
 
diff --git a/src/engine/types.h b/src/engine/types.h
index 7ccaa9f2fe..e53ed39387 100644
--- a/src/engine/types.h
+++ b/src/engine/types.h
@@ -1,6 +1,7 @@
-/*  Copyright 2019 Rene Rivera
+/*  Copyright 2019-2023 René Ferdinand Rivera Morell
  *  Distributed under the Boost Software License, Version 1.0.
- *  (See accompanying file LICENSE.txt or https://www.bfgroup.xyz/b2/LICENSE.txt)
+ *  (See accompanying file LICENSE.txt or
+ * https://www.bfgroup.xyz/b2/LICENSE.txt)
  */
 
 #ifndef B2_TYPES_H
@@ -14,8 +15,7 @@
 #include <mutex>
 #endif
 
-namespace b2
-{
+namespace b2 {
 using string_t = std::string;
 using int_t = int;
 using uint_t = unsigned int;
@@ -27,10 +27,11 @@ using scope_lock_t = std::unique_lock<std::mutex>;
 
 #else
 
-struct mutex_t {};
+struct mutex_t
+{};
 struct scope_lock_t
 {
-    inline scope_lock_t(mutex_t &) {}
+	inline scope_lock_t(mutex_t &) {}
 };
 
 #endif
diff --git a/src/engine/value.h b/src/engine/value.h
index b31e4f0c7c..0038f7845a 100644
--- a/src/engine/value.h
+++ b/src/engine/value.h
@@ -1,5 +1,5 @@
 /*
-Copyright 2022 René Ferdinand Rivera Morell
+Copyright 2022-2023 René Ferdinand Rivera Morell
 Distributed under the Boost Software License, Version 1.0.
 (See accompanying file LICENSE.txt or https://www.bfgroup.xyz/b2/LICENSE.txt)
 */
@@ -12,8 +12,10 @@ Distributed under the Boost Software License, Version 1.0.
 #include "strview.h"
 
 #include <cstdint>
+#include <cstdio>
 #include <cstring>
 #include <limits>
+#include <memory>
 #include <string>
 
 namespace b2 {
@@ -75,6 +77,21 @@ struct value
 	static void done();
 
 	inline bool has_value() const { return get_type() == type::null; }
+
+	template <typename T>
+	static inline value * as_string(T v)
+	{
+		return value::make(std::to_string(v));
+	}
+
+	template <typename... Args>
+	static inline value * format(const char * f, Args... args)
+	{
+		auto size = std::snprintf(nullptr, 0, f, args...);
+		std::unique_ptr<char[]> s(new char[size + 1]);
+		std::snprintf(s.get(), size + 1, f, args...);
+		return value::make(s.get(), size);
+	}
 };
 
 typedef value * value_ptr;
diff --git a/src/engine/w32_getreg.cpp b/src/engine/w32_getreg.cpp
index 4cbc9dd01e..2f5b0478ad 100644
--- a/src/engine/w32_getreg.cpp
+++ b/src/engine/w32_getreg.cpp
@@ -111,9 +111,8 @@ LIST * builtin_system_registry( FRAME * frame, int flags )
 
              case REG_DWORD:
                  {
-                     char buf[100];
-                     sprintf( buf, "%lu", *(PDWORD)data );
-                     result = list_push_back( result, object_new(buf) );
+                     result = list_push_back( result,
+                        b2::value::as_string( *(PDWORD)data ) );
                  }
                  break;