minimal-printf: Enable using a target configuration parameter

targets/targets.json

@@ -15,6 +15,7 @@
         "default_lib": "std",
         "bootloader_supported": false,
         "static_memory_defines": true,
+        "printf_lib": "std",
         "config": {
             "console-uart": {
                 "help": "Target has UART console on pins STDIO_UART_TX, STDIO_UART_RX. Value is only significant if target has SERIAL device.",

tools/test/toolchains/test_toolchains.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+# Copyright (c) 2019 Arm Limited and Contributors. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+"""Test the arm toolchain."""
+
+import os
+import sys
+
+import mock
+
+
+ROOT = os.path.abspath(
+    os.path.join(os.path.dirname(__file__), "..", "..", "..")
+)
+sys.path.insert(0, ROOT)
+
+from tools.toolchains.arm import ARM_STD, ARM_MICRO, ARMC6
+from tools.toolchains.gcc import GCC_ARM
+from tools.toolchains.iar import IAR
+
+
+class TestArmToolchain:
+    """Test Arm classes."""
+
+    def test_arm_minimal_printf(self):
+        """Test that linker flags are correctly added to an instance of ARM."""
+        mock_target = mock.MagicMock()
+        mock_target.core = "Cortex-M4"
+        mock_target.printf_lib = "minimal-printf"
+        mock_target.supported_toolchains = ["ARM", "uARM", "ARMC5"]
+
+        arm_std_obj = ARM_STD(mock_target)
+        arm_micro_obj = ARM_MICRO(mock_target)
+        arm_c6_obj = ARMC6(mock_target)
+
+        assert "-DMBED_MINIMAL_PRINTF" in arm_std_obj.flags["common"]
+        assert "-DMBED_MINIMAL_PRINTF" in arm_micro_obj.flags["common"]
+        assert "-DMBED_MINIMAL_PRINTF" in arm_c6_obj.flags["common"]
+
+
+class TestGccToolchain:
+    """Test the GCC class."""
+
+    def test_gcc_minimal_printf(self):
+        """Test that linker flags are correctly added to an instance of GCC_ARM."""
+        mock_target = mock.MagicMock()
+        mock_target.core = "Cortex-M4"
+        mock_target.printf_lib = "minimal-printf"
+        mock_target.supported_toolchains = ["GCC_ARM"]
+        mock_target.is_TrustZone_secure_target = False
+
+        gcc_obj = GCC_ARM(mock_target)
+
+        assert "-DMBED_MINIMAL_PRINTF" in gcc_obj.flags["common"]
+
+        minimal_printf_wraps = [
+            "-Wl,--wrap,printf",
+            "-Wl,--wrap,sprintf",
+            "-Wl,--wrap,snprintf",
+            "-Wl,--wrap,vprintf",
+            "-Wl,--wrap,vsprintf",
+            "-Wl,--wrap,vsnprintf",
+            "-Wl,--wrap,fprintf",
+            "-Wl,--wrap,vfprintf",
+        ]
+
+        assert all(
+            elem in gcc_obj.flags["ld"] for elem in minimal_printf_wraps
+        )
+
+
+class TestIarToolchain:
+    """Test the IAR class."""
+
+    def test_iar_minimal_printf(self):
+        """Test that linker flags are correctly added to an instance of GCC_ARM."""
+        mock_target = mock.MagicMock()
+        mock_target.core = "Cortex-M4"
+        mock_target.printf_lib = "minimal-printf"
+        mock_target.supported_toolchains = ["IAR"]
+        mock_target.is_TrustZone_secure_target = False
+
+        iar_obj = IAR(mock_target)
+
+        assert "-DMBED_MINIMAL_PRINTF" in iar_obj.flags["common"]

tools/toolchains/arm.py

@@ -81,6 +81,12 @@ def __init__(self, target, notify=None, macros=None,
             if "--library_type=microlib" not in self.flags['common']:
                 self.flags['common'].append("--library_type=microlib")
 
+        if (
+            target.printf_lib == "minimal-printf"
+            and "-DMBED_MINIMAL_PRINTF" not in self.flags['common']
+        ):
+            self.flags["common"].append("-DMBED_MINIMAL_PRINTF")
+
         cpu = {
             "Cortex-M0+": "Cortex-M0plus",
             "Cortex-M4F": "Cortex-M4.fp.sp",
@@ -568,6 +574,12 @@ def __init__(self, target, *args, **kwargs):
             if "--library_type=microlib" not in self.flags['asm']:
                 self.flags['asm'].append("--library_type=microlib")
 
+        if (
+            target.printf_lib == "minimal-printf"
+            and "-DMBED_MINIMAL_PRINTF" not in self.flags["common"]
+        ):
+            self.flags["common"].append("-DMBED_MINIMAL_PRINTF")
+
         if target.is_TrustZone_secure_target:
             if kwargs.get('build_dir', False):
                 # Output secure import library

tools/toolchains/gcc.py

@@ -58,6 +58,25 @@ def __init__(self, target,  notify=None, macros=None, build_profile=None,
             self.flags["common"].append("-DMBED_RTOS_SINGLE_THREAD")
             self.flags["ld"].append("--specs=nano.specs")
 
+        if target.printf_lib == "minimal-printf":
+            if "-DMBED_MINIMAL_PRINTF" not in self.flags['common']:
+                self.flags["common"].append("-DMBED_MINIMAL_PRINTF")
+
+            minimal_printf_wraps = [
+                "-Wl,--wrap,printf",
+                "-Wl,--wrap,sprintf",
+                "-Wl,--wrap,snprintf",
+                "-Wl,--wrap,vprintf",
+                "-Wl,--wrap,vsprintf",
+                "-Wl,--wrap,vsnprintf",
+                "-Wl,--wrap,fprintf",
+                "-Wl,--wrap,vfprintf",
+            ]
+
+            for minimal_printf_wrap in minimal_printf_wraps:
+                if minimal_printf_wrap not in self.flags["ld"]:
+                    self.flags["ld"].append(minimal_printf_wrap)
+
         self.cpu = []
         if target.is_TrustZone_secure_target:
             # Enable compiler security extensions

tools/toolchains/iar.py

@@ -69,6 +69,12 @@ def __init__(self, target, notify=None, macros=None, build_profile=None,
             define_string = self.make_ld_define("DOMAIN_NS", "0x1")
             self.flags["ld"].append(define_string)
 
+        if (
+            target.printf_lib == "minimal-printf"
+            and "-DMBED_MINIMAL_PRINTF" not in self.flags["common"]
+        ):
+            self.flags["common"].append("-DMBED_MINIMAL_PRINTF")
+
         core = target.core_without_NS
         cpu = {
             "Cortex-M7F": "Cortex-M7.fp.sp",