diff --git a/src/misc/CMakeLists.txt b/src/misc/CMakeLists.txt
--- a/src/misc/CMakeLists.txt
+++ b/src/misc/CMakeLists.txt
@@ -11,5 +11,4 @@ add_files(
     getoptdata.h
     hashtable.hpp
     lrucache.hpp
-    str.hpp
 )
diff --git a/src/misc/array.hpp b/src/misc/array.hpp
--- a/src/misc/array.hpp
+++ b/src/misc/array.hpp
@@ -11,7 +11,7 @@
 #define ARRAY_HPP
 
 #include "fixedsizearray.hpp"
-#include "str.hpp"
+#include "../string_func.h"
 
 /**
  * Flexible array with size limit. Implemented as fixed size
@@ -103,14 +103,14 @@ public:
 	 */
 	template <typename D> void Dump(D &dmp) const
 	{
-		dmp.WriteLine("capacity = %d", Tcapacity);
+		dmp.WriteValue("capacity", Tcapacity);
 		uint num_items = Length();
-		dmp.WriteLine("num_items = %d", num_items);
-		CStrA name;
+		dmp.WriteValue("num_items", num_items);
 		for (uint i = 0; i < num_items; i++) {
 			const T &item = (*this)[i];
-			name.Format("item[%d]", i);
-			dmp.WriteStructT(name.Data(), &item);
+			char name[32];
+			seprintf(name, lastof(name), "item[%d]", i);
+			dmp.WriteStructT(name, &item);
 		}
 	}
 };
diff --git a/src/misc/dbg_helpers.cpp b/src/misc/dbg_helpers.cpp
--- a/src/misc/dbg_helpers.cpp
+++ b/src/misc/dbg_helpers.cpp
@@ -10,6 +10,10 @@
 #include "../stdafx.h"
 #include "../rail_map.h"
 #include "dbg_helpers.h"
+#include "blob.hpp"
+
+#include <sstream>
+#include <iomanip>
 
 #include "../safeguards.h"
 
@@ -20,19 +24,15 @@ static const char * const trackdir_names
 };
 
 /** Return name of given Trackdir. */
-CStrA ValueStr(Trackdir td)
+std::string ValueStr(Trackdir td)
 {
-	CStrA out;
-	out.Format("%d (%s)", td, ItemAtT(td, trackdir_names, "UNK", INVALID_TRACKDIR, "INV"));
-	return out.Transfer();
+	return std::to_string(td) + " (" + ItemAtT(td, trackdir_names, "UNK", INVALID_TRACKDIR, "INV") + ")";
 }
 
 /** Return composed name of given TrackdirBits. */
-CStrA ValueStr(TrackdirBits td_bits)
+std::string ValueStr(TrackdirBits td_bits)
 {
-	CStrA out;
-	out.Format("%d (%s)", td_bits, ComposeNameT(td_bits, trackdir_names, "UNK", INVALID_TRACKDIR_BIT, "INV").Data());
-	return out.Transfer();
+	return std::to_string(td_bits) + " (" + ComposeNameT(td_bits, trackdir_names, "UNK", INVALID_TRACKDIR_BIT, "INV") + ")";
 }
 
 
@@ -42,11 +42,9 @@ static const char * const diagdir_names[
 };
 
 /** Return name of given DiagDirection. */
-CStrA ValueStr(DiagDirection dd)
+std::string ValueStr(DiagDirection dd)
 {
-	CStrA out;
-	out.Format("%d (%s)", dd, ItemAtT(dd, diagdir_names, "UNK", INVALID_DIAGDIR, "INV"));
-	return out.Transfer();
+	return std::to_string(dd) + " (" + ItemAtT(dd, diagdir_names, "UNK", INVALID_DIAGDIR, "INV") + ")";
 }
 
 
@@ -56,20 +54,19 @@ static const char * const signal_type_na
 };
 
 /** Return name of given SignalType. */
-CStrA ValueStr(SignalType t)
+std::string ValueStr(SignalType t)
 {
-	CStrA out;
-	out.Format("%d (%s)", t, ItemAtT(t, signal_type_names, "UNK"));
-	return out.Transfer();
+	return std::to_string(t) + " (" + ItemAtT(t, signal_type_names, "UNK") + ")";
 }
 
 
 /** Translate TileIndex into string. */
-CStrA TileStr(TileIndex tile)
+std::string TileStr(TileIndex tile)
 {
-	CStrA out;
-	out.Format("0x%04X (%d, %d)", tile, TileX(tile), TileY(tile));
-	return out.Transfer();
+	std::stringstream ss;
+	ss << "0x" << std::setfill('0') << std::setw(4) << std::hex << tile; // 0x%04X
+	ss << " (" << TileX(tile) << ", " << TileY(tile) << ")";
+	return ss.str();
 }
 
 /**
@@ -81,21 +78,21 @@ CStrA TileStr(TileIndex tile)
 }
 
 /** Return structured name of the current class/structure. */
-CStrA DumpTarget::GetCurrentStructName()
+std::string DumpTarget::GetCurrentStructName()
 {
-	CStrA out;
+	std::string out;
 	if (!m_cur_struct.empty()) {
 		/* we are inside some named struct, return its name */
 		out = m_cur_struct.top();
 	}
-	return out.Transfer();
+	return out;
 }
 
 /**
  * Find the given instance in our anti-recursion repository.
  * Return true and set name when object was found.
  */
-bool DumpTarget::FindKnownName(size_t type_id, const void *ptr, CStrA &name)
+bool DumpTarget::FindKnownName(size_t type_id, const void *ptr, std::string &name)
 {
 	KNOWN_NAMES::const_iterator it = m_known_names.find(KnownStructKey(type_id, ptr));
 	if (it != m_known_names.end()) {
@@ -111,33 +108,29 @@ void DumpTarget::WriteIndent()
 {
 	int num_spaces = 2 * m_indent;
 	if (num_spaces > 0) {
-		memset(m_out.GrowSizeNC(num_spaces), ' ', num_spaces);
+		m_out += std::string(num_spaces, ' ');
 	}
 }
 
-/** Write a line with indent at the beginning and \<LF\> at the end. */
-void DumpTarget::WriteLine(const char *format, ...)
+/** Write 'name = value' with indent and new-line. */
+void DumpTarget::WriteValue(const char *name, int value)
 {
 	WriteIndent();
-	va_list args;
-	va_start(args, format);
-	m_out.AddFormatL(format, args);
-	va_end(args);
-	m_out.AppendStr("\n");
+	m_out += std::string(name) + " = " + std::to_string(value) + "\n";
 }
 
 /** Write 'name = value' with indent and new-line. */
 void DumpTarget::WriteValue(const char *name, const char *value_str)
 {
 	WriteIndent();
-	m_out.AddFormat("%s = %s\n", name, value_str);
+	m_out += std::string(name) + " = " + value_str + "\n";
 }
 
 /** Write name & TileIndex to the output. */
 void DumpTarget::WriteTile(const char *name, TileIndex tile)
 {
 	WriteIndent();
-	m_out.AddFormat("%s = %s\n", name, TileStr(tile).Data());
+	m_out += std::string(name) + " = " + TileStr(tile) + "\n";
 }
 
 /**
@@ -146,12 +139,12 @@ void DumpTarget::WriteTile(const char *n
 void DumpTarget::BeginStruct(size_t type_id, const char *name, const void *ptr)
 {
 	/* make composite name */
-	CStrA cur_name = GetCurrentStructName().Transfer();
-	if (cur_name.Size() > 0) {
+	std::string cur_name = GetCurrentStructName();
+	if (cur_name.size() > 0) {
 		/* add name delimiter (we use structured names) */
-		cur_name.AppendStr(".");
+		cur_name += ".";
 	}
-	cur_name.AppendStr(name);
+	cur_name += name;
 
 	/* put the name onto stack (as current struct name) */
 	m_cur_struct.push(cur_name);
@@ -160,7 +153,7 @@ void DumpTarget::BeginStruct(size_t type
 	m_known_names.insert(KNOWN_NAMES::value_type(KnownStructKey(type_id, ptr), cur_name));
 
 	WriteIndent();
-	m_out.AddFormat("%s = {\n", name);
+	m_out += std::string(name) + " = {\n";
 	m_indent++;
 }
 
@@ -171,7 +164,7 @@ void DumpTarget::EndStruct()
 {
 	m_indent--;
 	WriteIndent();
-	m_out.AddFormat("}\n");
+	m_out += "}\n";
 
 	/* remove current struct name from the stack */
 	m_cur_struct.pop();
diff --git a/src/misc/dbg_helpers.h b/src/misc/dbg_helpers.h
--- a/src/misc/dbg_helpers.h
+++ b/src/misc/dbg_helpers.h
@@ -12,8 +12,7 @@
 
 #include <map>
 #include <stack>
-
-#include "str.hpp"
+#include <string>
 
 #include "../direction_type.h"
 #include "../signal_type.h"
@@ -67,9 +66,9 @@ inline typename ArrayT<T>::item_t ItemAt
  * or t_unk when index is out of bounds.
  */
 template <typename E, typename T>
-inline CStrA ComposeNameT(E value, T &t, const char *t_unk, E val_inv, const char *name_inv)
+inline std::string ComposeNameT(E value, T &t, const char *t_unk, E val_inv, const char *name_inv)
 {
-	CStrA out;
+	std::string out;
 	if (value == val_inv) {
 		out = name_inv;
 	} else if (value == 0) {
@@ -77,18 +76,22 @@ inline CStrA ComposeNameT(E value, T &t,
 	} else {
 		for (size_t i = 0; i < ArrayT<T>::length; i++) {
 			if ((value & (1 << i)) == 0) continue;
-			out.AddFormat("%s%s", (out.Size() > 0 ? "+" : ""), (const char*)t[i]);
+			out += (!out.empty() ? "+" : "");
+			out += t[i];
 			value &= ~(E)(1 << i);
 		}
-		if (value != 0) out.AddFormat("%s%s", (out.Size() > 0 ? "+" : ""), t_unk);
+		if (value != 0) {
+			out += (!out.empty() ? "+" : "");
+			out += t_unk;
+		}
 	}
-	return out.Transfer();
+	return out;
 }
 
-CStrA ValueStr(Trackdir td);
-CStrA ValueStr(TrackdirBits td_bits);
-CStrA ValueStr(DiagDirection dd);
-CStrA ValueStr(SignalType t);
+std::string ValueStr(Trackdir td);
+std::string ValueStr(TrackdirBits td_bits);
+std::string ValueStr(DiagDirection dd);
+std::string ValueStr(SignalType t);
 
 /** Class that represents the dump-into-string target. */
 struct DumpTarget {
@@ -118,31 +121,31 @@ struct DumpTarget {
 		}
 	};
 
-	typedef std::map<KnownStructKey, CStrA> KNOWN_NAMES;
+	typedef std::map<KnownStructKey, std::string> KNOWN_NAMES;
 
-	CStrA              m_out;         ///< the output string
-	int                m_indent;      ///< current indent/nesting level
-	std::stack<CStrA>  m_cur_struct;  ///< here we will track the current structure name
-	KNOWN_NAMES        m_known_names; ///< map of known object instances and their structured names
+	std::string m_out;                    ///< the output string
+	int m_indent;                         ///< current indent/nesting level
+	std::stack<std::string> m_cur_struct; ///< here we will track the current structure name
+	KNOWN_NAMES m_known_names;            ///< map of known object instances and their structured names
 
 	DumpTarget()
 		: m_indent(0)
 	{}
 
 	static size_t& LastTypeId();
-	CStrA GetCurrentStructName();
-	bool FindKnownName(size_t type_id, const void *ptr, CStrA &name);
+	std::string GetCurrentStructName();
+	bool FindKnownName(size_t type_id, const void *ptr, std::string &name);
 
 	void WriteIndent();
 
-	void CDECL WriteLine(const char *format, ...) WARN_FORMAT(2, 3);
+	void WriteValue(const char *name, int value);
 	void WriteValue(const char *name, const char *value_str);
 	void WriteTile(const char *name, TileIndex t);
 
 	/** Dump given enum value (as a number and as named value) */
 	template <typename E> void WriteEnumT(const char *name, E e)
 	{
-		WriteValue(name, ValueStr(e).Data());
+		WriteValue(name, ValueStr(e).c_str());
 	}
 
 	void BeginStruct(size_t type_id, const char *name, const void *ptr);
@@ -155,13 +158,14 @@ struct DumpTarget {
 
 		if (s == nullptr) {
 			/* No need to dump nullptr struct. */
-			WriteLine("%s = <null>", name);
+			WriteValue(name, "<null>");
 			return;
 		}
-		CStrA known_as;
+		std::string known_as;
 		if (FindKnownName(type_id, s, known_as)) {
 			/* We already know this one, no need to dump it. */
-			WriteLine("%s = known_as.%s", name, known_as.Data());
+			std::string known_as_str = std::string("known_as.") + name;
+			WriteValue(name, known_as_str.c_str());
 		} else {
 			/* Still unknown, dump it */
 			BeginStruct(type_id, name, s);
diff --git a/src/misc/str.hpp b/src/misc/str.hpp
deleted file mode 100644
--- a/src/misc/str.hpp
+++ /dev/null
@@ -1,149 +0,0 @@
-/*
- * This file is part of OpenTTD.
- * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
- * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
- */
-
-/** @file str.hpp String formatting? */
-
-#ifndef STR_HPP
-#define STR_HPP
-
-#include <errno.h>
-#include <stdarg.h>
-#include "blob.hpp"
-#include "../core/math_func.hpp"
-#include "../string_func.h"
-
-/** Blob based case sensitive ANSI/UTF-8 string */
-struct CStrA : public CBlobT<char>
-{
-	typedef CBlobT<char> base;                    ///< base class
-
-	/** Create an empty CStrT */
-	inline CStrA()
-	{
-	}
-
-	/** Copy constructor */
-	inline CStrA(const CStrA &src) : base(src)
-	{
-		base::FixTail();
-	}
-
-	/** Take over ownership constructor */
-	inline CStrA(const OnTransfer &ot)
-		: base(ot)
-	{
-	}
-
-	/** Grow the actual buffer and fix the trailing zero at the end. */
-	inline char *GrowSizeNC(uint count)
-	{
-		char *ret = base::GrowSizeNC(count);
-		base::FixTail();
-		return ret;
-	}
-
-	/** Append zero-ended C string. */
-	inline void AppendStr(const char *str)
-	{
-		if (!StrEmpty(str)) {
-			base::AppendRaw(str, strlen(str));
-			base::FixTail();
-		}
-	}
-
-	/** Append another CStrA. */
-	inline void Append(const CStrA &src)
-	{
-		if (src.Length() > 0) {
-			base::AppendRaw(src);
-			base::FixTail();
-		}
-	}
-
-	/** Assignment from C string. */
-	inline CStrA &operator=(const char *src)
-	{
-		base::Clear();
-		AppendStr(src);
-		return *this;
-	}
-
-	/** Assignment from another CStrA. */
-	inline CStrA &operator=(const CStrA &src)
-	{
-		if (&src != this) {
-			base::Clear();
-			base::AppendRaw(src.Data(), src.Size());
-			base::FixTail();
-		}
-		return *this;
-	}
-
-	/** Lower-than operator (to support stl collections) */
-	inline bool operator<(const CStrA &other) const
-	{
-		return strcmp(base::Data(), other.Data()) < 0;
-	}
-
-	/** Add formatted string (like vsprintf) at the end of existing contents. */
-	int AddFormatL(const char *format, va_list args) WARN_FORMAT(2, 0)
-	{
-		size_t addSize = std::max<size_t>(strlen(format), 16);
-		addSize += addSize / 2;
-		int ret;
-		int err = 0;
-		for (;;) {
-			char *buf = MakeFreeSpace(addSize);
-			ret = vseprintf(buf, buf + base::GetReserve() - 1, format, args);
-			if (ret >= (int)base::GetReserve()) {
-				/* Greater return than given count means needed buffer size. */
-				addSize = ret + 1;
-				continue;
-			}
-			if (ret >= 0) {
-				/* success */
-				break;
-			}
-			err = errno;
-			if (err != ERANGE && err != ENOENT && err != 0) {
-				/* some strange failure */
-				break;
-			}
-			/* small buffer (M$ implementation) */
-			addSize *= 2;
-		}
-		if (ret > 0) {
-			GrowSizeNC(ret);
-		} else {
-			base::FixTail();
-		}
-		return ret;
-	}
-
-	/** Add formatted string (like sprintf) at the end of existing contents. */
-	int CDECL WARN_FORMAT(2, 3) AddFormat(const char *format, ...)
-	{
-		va_list args;
-		va_start(args, format);
-		int ret = AddFormatL(format, args);
-		va_end(args);
-		return ret;
-	}
-
-	/** Assign formatted string (like sprintf). */
-	int CDECL WARN_FORMAT(2, 3) Format(const char *format, ...)
-	{
-		base::Free();
-		va_list args;
-		va_start(args, format);
-		int ret = AddFormatL(format, args);
-		va_end(args);
-		return ret;
-	}
-};
-
-#endif /* STR_HPP */
diff --git a/src/pathfinder/yapf/yapf.hpp b/src/pathfinder/yapf/yapf.hpp
--- a/src/pathfinder/yapf/yapf.hpp
+++ b/src/pathfinder/yapf/yapf.hpp
@@ -19,7 +19,6 @@
 //#define inline inline
 
 #include "../../misc/blob.hpp"
-#include "../../misc/str.hpp"
 #include "../../misc/fixedsizearray.hpp"
 #include "../../misc/array.hpp"
 #include "../../misc/hashtable.hpp"
diff --git a/src/pathfinder/yapf/yapf_base.hpp b/src/pathfinder/yapf/yapf_base.hpp
--- a/src/pathfinder/yapf/yapf_base.hpp
+++ b/src/pathfinder/yapf/yapf_base.hpp
@@ -317,7 +317,7 @@ public:
 	void DumpBase(DumpTarget &dmp) const
 	{
 		dmp.WriteStructT("m_nodes", &m_nodes);
-		dmp.WriteLine("m_num_steps = %d", m_num_steps);
+		dmp.WriteValue("m_num_steps", m_num_steps);
 	}
 
 	/* methods that should be implemented at derived class Types::Tpf (derived from CYapfBaseT) */
diff --git a/src/pathfinder/yapf/yapf_node.hpp b/src/pathfinder/yapf/yapf_node.hpp
--- a/src/pathfinder/yapf/yapf_node.hpp
+++ b/src/pathfinder/yapf/yapf_node.hpp
@@ -126,8 +126,8 @@ struct CYapfNodeT {
 	{
 		dmp.WriteStructT("m_key", &m_key);
 		dmp.WriteStructT("m_parent", m_parent);
-		dmp.WriteLine("m_cost = %d", m_cost);
-		dmp.WriteLine("m_estimate = %d", m_estimate);
+		dmp.WriteValue("m_cost", m_cost);
+		dmp.WriteValue("m_estimate", m_estimate);
 	}
 };
 
diff --git a/src/pathfinder/yapf/yapf_node_rail.hpp b/src/pathfinder/yapf/yapf_node_rail.hpp
--- a/src/pathfinder/yapf/yapf_node_rail.hpp
+++ b/src/pathfinder/yapf/yapf_node_rail.hpp
@@ -109,7 +109,7 @@ struct CYapfRailSegment
 		dmp.WriteStructT("m_key", &m_key);
 		dmp.WriteTile("m_last_tile", m_last_tile);
 		dmp.WriteEnumT("m_last_td", m_last_td);
-		dmp.WriteLine("m_cost = %d", m_cost);
+		dmp.WriteValue("m_cost", m_cost);
 		dmp.WriteTile("m_last_signal_tile", m_last_signal_tile);
 		dmp.WriteEnumT("m_last_signal_td", m_last_signal_td);
 		dmp.WriteEnumT("m_end_segment_reason", m_end_segment_reason);
@@ -207,10 +207,10 @@ struct CYapfRailNodeT
 	{
 		base::Dump(dmp);
 		dmp.WriteStructT("m_segment", m_segment);
-		dmp.WriteLine("m_num_signals_passed = %d", m_num_signals_passed);
-		dmp.WriteLine("m_targed_seen = %s", flags_u.flags_s.m_targed_seen ? "Yes" : "No");
-		dmp.WriteLine("m_choice_seen = %s", flags_u.flags_s.m_choice_seen ? "Yes" : "No");
-		dmp.WriteLine("m_last_signal_was_red = %s", flags_u.flags_s.m_last_signal_was_red ? "Yes" : "No");
+		dmp.WriteValue("m_num_signals_passed", m_num_signals_passed);
+		dmp.WriteValue("m_targed_seen", flags_u.flags_s.m_targed_seen ? "Yes" : "No");
+		dmp.WriteValue("m_choice_seen", flags_u.flags_s.m_choice_seen ? "Yes" : "No");
+		dmp.WriteValue("m_last_signal_was_red", flags_u.flags_s.m_last_signal_was_red ? "Yes" : "No");
 		dmp.WriteEnumT("m_last_red_signal_type", m_last_red_signal_type);
 	}
 };
diff --git a/src/pathfinder/yapf/yapf_rail.cpp b/src/pathfinder/yapf/yapf_rail.cpp
--- a/src/pathfinder/yapf/yapf_rail.cpp
+++ b/src/pathfinder/yapf/yapf_rail.cpp
@@ -28,8 +28,8 @@ template <typename Tpf> void DumpState(T
 	FILE *f2 = fopen("yapf2.txt", "wt");
 	assert(f1 != nullptr);
 	assert(f2 != nullptr);
-	fwrite(dmp1.m_out.Data(), 1, dmp1.m_out.Size(), f1);
-	fwrite(dmp2.m_out.Data(), 1, dmp2.m_out.Size(), f2);
+	fwrite(dmp1.m_out.c_str(), 1, dmp1.m_out.size(), f1);
+	fwrite(dmp2.m_out.c_str(), 1, dmp2.m_out.size(), f2);
 	fclose(f1);
 	fclose(f2);
 }
diff --git a/src/pathfinder/yapf/yapf_type.hpp b/src/pathfinder/yapf/yapf_type.hpp
--- a/src/pathfinder/yapf/yapf_type.hpp
+++ b/src/pathfinder/yapf/yapf_type.hpp
@@ -10,6 +10,9 @@
 #ifndef YAPF_TYPE_HPP
 #define YAPF_TYPE_HPP
 
+#include <iomanip>
+#include <sstream>
+
 /* Enum used in PfCalcCost() to see why was the segment closed. */
 enum EndSegmentReason {
 	/* The following reasons can be saved into cached segment */
@@ -66,7 +69,7 @@ enum EndSegmentReasonBits {
 
 DECLARE_ENUM_AS_BIT_SET(EndSegmentReasonBits)
 
-inline CStrA ValueStr(EndSegmentReasonBits bits)
+inline std::string ValueStr(EndSegmentReasonBits bits)
 {
 	static const char * const end_segment_reason_names[] = {
 		"DEAD_END", "RAIL_TYPE", "INFINITE_LOOP", "SEGMENT_TOO_LONG", "CHOICE_FOLLOWS",
@@ -74,9 +77,10 @@ inline CStrA ValueStr(EndSegmentReasonBi
 		"PATH_TOO_LONG", "FIRST_TWO_WAY_RED", "LOOK_AHEAD_END", "TARGET_REACHED"
 	};
 
-	CStrA out;
-	out.Format("0x%04X (%s)", bits, ComposeNameT(bits, end_segment_reason_names, "UNK", ESRB_NONE, "NONE").Data());
-	return out.Transfer();
+	std::stringstream ss;
+	ss << "0x" << std::setfill('0') << std::setw(4) << std::hex << bits; // 0x%04X
+	ss << " (" << ComposeNameT(bits, end_segment_reason_names, "UNK", ESRB_NONE, "NONE") << ")";
+	return ss.str();
 }
 
 #endif /* YAPF_TYPE_HPP */