pkg/mpaland-printf: Add alternative stdio as package

This packs the stdio implementation from [1] as alternative to
what the used standard C lib provides with the intent to provide a
thread-safe, smaller, and more feature-complete alternative on
newlib targets.

Compared to `newlib_nano` this reduces `.text` by a bit more than 200 B
while adding support for standard format specifiers such as `RPIu8`,
`PRIu16`, `PRIu64`, `%z`, and `%t`.

Note that `newlib_nano`'s stdio can be thread-safe in reentrant mode
at the cost of RAM (per thread) and latency. Especially the increase
in latency can be prohibitive when real time requirements need to be
met.

[1]: https://github.com/mpaland/printf

pkg/mpaland-printf/Makefile

@@ -0,0 +1,10 @@
+PKG_NAME=mpaland-printf
+PKG_URL=https://github.com/mpaland/printf
+# 4.0.0
+PKG_VERSION=0dd4b64bc778bf55229428cefccba4c0a81f384b
+PKG_LICENSE=MIT
+
+include $(RIOTBASE)/pkg/pkg.mk
+
+all:
+	$(QQ)"$(MAKE)" -C $(PKG_SOURCE_DIR) -f $(RIOTPKG)/$(PKG_NAME)/$(PKG_NAME).mk

pkg/mpaland-printf/Makefile.dep

@@ -0,0 +1,4 @@
+# mpaland's printf does not implement non-standard format specifiers. For
+# AVR MCUs we do need the ability to print from PROGMEM, though. Hence, this
+# is not compatible with AVR MCUs.
+FEATURES_BLACKLIST += arch_avr8

pkg/mpaland-printf/Makefile.include

@@ -0,0 +1,9 @@
+# wrap stdio functions to use mpaland's printf instead of the one from the
+# standard C lib
+LINKFLAGS += -Wl,-wrap=printf
+LINKFLAGS += -Wl,-wrap=sprintf
+LINKFLAGS += -Wl,-wrap=snprintf
+LINKFLAGS += -Wl,-wrap=vprintf
+LINKFLAGS += -Wl,-wrap=vsnprintf
+LINKFLAGS += -Wl,-wrap=putchar
+LINKFLAGS += -Wl,-wrap=puts

pkg/mpaland-printf/doc.txt

@@ -0,0 +1,29 @@
+/**
+ * @defgroup    pkg_mpaland-printf   mpaland's printf
+ * @ingroup     pkg
+ * @brief       mpaland's printf implementation is a lean, thread-safe and
+ *              feature-complete printf implementation
+ *
+ * # License
+ *
+ * Licensed under the MIT license.
+ *
+ * # Usage
+ *
+ * Add `USEPKG += mpaland-printf` to the application's `Makefile` or compile
+ * using `USEPKG=mpaland-printf make BOARD=<BOARD> -C <APP_DIR>`.
+ *
+ * # Features
+ *
+ * The package implements all standard format specifiers. However, support
+ * for floating point is disabled by default due to the immense ROM overhead
+ * on MCUs without FPU.
+ *
+ * @note    Support for floating point formatting can be enabled
+ *          `printf_float` module, e.g. by adding
+ *          `USEMODULE += printf_float` to the application's `Makefile`.
+ * @note    Support for non-standard format specifiers such as needed for
+ *          printing from flash on AVR MCUs are not implemented.
+ *
+ * @see         https://github.com/mpaland/printf
+ */

pkg/mpaland-printf/mpaland-printf.mk

@@ -0,0 +1,7 @@
+MODULE := mpaland-printf
+
+SRC := \
+  printf.c \
+  #
+
+include $(RIOTBASE)/Makefile.base

pkg/mpaland-printf/patches/0001-RIOT-integration.patch

@@ -0,0 +1,50 @@
+From 875a37ec418c41ffd060e39b2153357a32175ac5 Mon Sep 17 00:00:00 2001
+From: Marian Buschsieweke <[email protected]>
+Date: Sat, 11 May 2024 17:51:01 +0200
+Subject: [PATCH 1/2] RIOT integration
+
+Use stdio_write() from stdio_base.h for output
+---
+ printf.c | 8 ++++++++
+ printf.h | 2 +-
+ 2 files changed, 9 insertions(+), 1 deletion(-)
+
+diff --git a/printf.c b/printf.c
+index 8a700ad..fd83570 100644
+--- a/printf.c
++++ b/printf.c
+@@ -34,6 +34,7 @@
+ #include <stdint.h>
+
+ #include "printf.h"
++#include "stdio_base.h"
+
+
+ // define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
+@@ -912,3 +913,10 @@ int fctprintf(void (*out)(char character, void* arg), void* arg, const char* for
+   va_end(va);
+   return ret;
+ }
++
++
++/* RIOT integration: Use stdio_write for output */
++static void _putchar(char character)
++{
++    stdio_write(&character, sizeof(character));
++}
+diff --git a/printf.h b/printf.h
+index 6075bc2..e185911 100644
+--- a/printf.h
++++ b/printf.h
+@@ -46,7 +46,7 @@ extern "C" {
+  * This function is declared here only. You have to write your custom implementation somewhere
+  * \param character Character to output
+  */
+-void _putchar(char character);
++static void _putchar(char character);
+
+
+ /**
+-- 
+2.45.0
+

pkg/mpaland-printf/patches/0002-Wrapper-targets-Add-endpoints-for-Wl-wrap.patch

@@ -0,0 +1,66 @@
+From 6fcc450e49791de23446b26cb4b2dc388590c763 Mon Sep 17 00:00:00 2001
+From: Marian Buschsieweke <[email protected]>
+Date: Sat, 11 May 2024 17:51:38 +0200
+Subject: [PATCH 2/2] Wrapper targets: Add endpoints for -Wl,wrap=...
+
+This adds aliases needed to wrap printf() and friends.
+---
+ printf.c | 38 ++++++++++++++++++++++++++++++++++++++
+ 1 file changed, 38 insertions(+)
+
+diff --git a/printf.c b/printf.c
+index fd83570..4694bab 100644
+--- a/printf.c
++++ b/printf.c
+@@ -32,6 +32,7 @@
+
+ #include <stdbool.h>
+ #include <stdint.h>
++#include <string.h>
+
+ #include "printf.h"
+ #include "stdio_base.h"
+@@ -920,3 +921,40 @@ static void _putchar(char character)
+ {
+     stdio_write(&character, sizeof(character));
+ }
++
++
++/* provide entry points for linker to redirect stdio */
++__attribute__((alias("printf_")))
++int __wrap_printf(const char* format, ...);
++
++
++__attribute__((alias("sprintf_")))
++int __wrap_sprintf(char* buffer, const char* format, ...);
++
++
++__attribute__((alias("snprintf_")))
++int __wrap_snprintf(char* buffer, size_t count, const char* format, ...);
++
++
++__attribute__((alias("vprintf_")))
++int __wrap_vprintf(const char* format, va_list va);
++
++
++__attribute__((alias("vsnprintf_")))
++int __wrap_vsnprintf(char* buffer, size_t count, const char* format, va_list va);
++
++
++int __wrap_putchar(int c)
++{
++    _putchar((char)c);
++    return 1;
++}
++
++
++int __wrap_puts(const char *s)
++{
++    size_t len = strlen(s);
++    stdio_write(s, len);
++    stdio_write("\n", 1);
++    return len + 1;
++}
+-- 
+2.45.0
+

pkg/mpaland-printf/patches/0003-RIOT-integration-Enable-floating-support-based-on-mo.patch

@@ -0,0 +1,131 @@
+From 8436eab79cda1de6e81d5d1d00c379036efa3900 Mon Sep 17 00:00:00 2001
+From: Marian Buschsieweke <[email protected]>
+Date: Sat, 11 May 2024 18:38:51 +0200
+Subject: [PATCH 3/3] RIOT integration: Enable floating support based on module
+ selection
+
+---
+ printf.c | 94 ++++++++++++++++++++++++++++----------------------------
+ 1 file changed, 47 insertions(+), 47 deletions(-)
+
+diff --git a/printf.c b/printf.c
+index e06c9aa..c4980e3 100644
+--- a/printf.c
++++ b/printf.c
+@@ -32,10 +32,10 @@
+
+ #include <stdbool.h>
+ #include <stdint.h>
+-#include <string.h>
++#include <string.h>
+
+ #include "printf.h"
+-#include "stdio_base.h"
++#include "stdio_base.h"
+
+
+ // define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
+@@ -62,7 +62,7 @@
+
+ // support for the floating point type (%f)
+ // default: activated
+-#ifndef PRINTF_DISABLE_SUPPORT_FLOAT
++#ifdef MODULE_PRINTF_FLOAT
+ #define PRINTF_SUPPORT_FLOAT
+ #endif
+
+@@ -914,47 +914,47 @@ int fctprintf(void (*out)(char character, void* arg), void* arg, const char* for
+   va_end(va);
+   return ret;
+ }
+-
+-
+-/* RIOT integration: Use stdio_write for output */
+-static void _putchar(char character)
+-{
+-    stdio_write(&character, sizeof(character));
+-}
+-
+-
+-/* provide entry points for linker to redirect stdio */
+-__attribute__((alias("printf_")))
+-int __wrap_printf(const char* format, ...);
+-
+-
+-__attribute__((alias("sprintf_")))
+-int __wrap_sprintf(char* buffer, const char* format, ...);
+-
+-
+-__attribute__((alias("snprintf_")))
+-int __wrap_snprintf(char* buffer, size_t count, const char* format, ...);
+-
+-
+-__attribute__((alias("vprintf_")))
+-int __wrap_vprintf(const char* format, va_list va);
+-
+-
+-__attribute__((alias("vsnprintf_")))
+-int __wrap_vsnprintf(char* buffer, size_t count, const char* format, va_list va);
+-
+-
+-int __wrap_putchar(int c)
+-{
+-    _putchar((char)c);
+-    return 1;
+-}
+-
+-
+-int __wrap_puts(const char *s)
+-{
+-    size_t len = strlen(s);
+-    stdio_write(s, len);
+-    stdio_write("\n", 1);
+-    return len + 1;
+-}
++
++
++/* RIOT integration: Use stdio_write for output */
++static void _putchar(char character)
++{
++    stdio_write(&character, sizeof(character));
++}
++
++
++/* provide entry points for linker to redirect stdio */
++__attribute__((alias("printf_")))
++int __wrap_printf(const char* format, ...);
++
++
++__attribute__((alias("sprintf_")))
++int __wrap_sprintf(char* buffer, const char* format, ...);
++
++
++__attribute__((alias("snprintf_")))
++int __wrap_snprintf(char* buffer, size_t count, const char* format, ...);
++
++
++__attribute__((alias("vprintf_")))
++int __wrap_vprintf(const char* format, va_list va);
++
++
++__attribute__((alias("vsnprintf_")))
++int __wrap_vsnprintf(char* buffer, size_t count, const char* format, va_list va);
++
++
++int __wrap_putchar(int c)
++{
++    _putchar((char)c);
++    return 1;
++}
++
++
++int __wrap_puts(const char *s)
++{
++    size_t len = strlen(s);
++    stdio_write(s, len);
++    stdio_write("\n", 1);
++    return len + 1;
++}
+-- 
+2.45.0
+

pkg/mpaland-printf/patches/0004-Fix-parsing-of-int8_t.patch

@@ -0,0 +1,28 @@
+From 24d4f4ef60aaaef3c471eb248799ebefde33cc03 Mon Sep 17 00:00:00 2001
+From: Marian Buschsieweke <[email protected]>
+Date: Sat, 11 May 2024 22:42:21 +0200
+Subject: [PATCH 4/4] Fix parsing of `int8_t`
+
+The code assumes that `char` is signed, but the C standard allows
+`char` to be either signed or unsigned. Instead, `singed char` and
+`unsigned char` need to be used for portable code.
+---
+ printf.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/printf.c b/printf.c
+index 5266cf7..440cfa6 100644
+--- a/printf.c
++++ b/printf.c
+@@ -734,7 +734,7 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
+             idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
+           }
+           else {
+-            const int value = (flags & FLAGS_CHAR) ? (char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int);
++            const int value = (flags & FLAGS_CHAR) ? (signed char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int);
+             idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
+           }
+         }
+-- 
+2.45.0
+