RIOT-OS · maribu · Sep 17, 2025 · Sep 17, 2025 · Sep 17, 2025 · Sep 17, 2025
@@ -5,6 +5,7 @@ FEATURES_PROVIDED += arch_32bit
 FEATURES_PROVIDED += arch_arm
 FEATURES_PROVIDED += arch_arm7
 FEATURES_PROVIDED += cpp
+FEATURES_PROVIDED += float_math
 FEATURES_PROVIDED += libstdcpp
 FEATURES_PROVIDED += newlib
 FEATURES_PROVIDED += periph_pm

@@ -3,17 +3,19 @@ include $(RIOTCPU)/avr8_common/Makefile.features
 # common feature are defined in avr8_common/Makefile.features
 # Only add Additional features
 
-FEATURES_PROVIDED += cpu_core_atmega
 FEATURES_PROVIDED += atmega_pcint0
+FEATURES_PROVIDED += cpu_core_atmega
+FEATURES_PROVIDED += float_math
 FEATURES_PROVIDED += periph_eeprom
-FEATURES_PROVIDED += periph_gpio periph_gpio_irq
 FEATURES_PROVIDED += periph_gpio_ll
 FEATURES_PROVIDED += periph_gpio_ll_input_pull_up
 FEATURES_PROVIDED += periph_gpio_ll_irq
 FEATURES_PROVIDED += periph_gpio_ll_irq_edge_triggered_both
 FEATURES_PROVIDED += periph_gpio_ll_irq_level_triggered_low
 FEATURES_PROVIDED += periph_gpio_ll_irq_unmask
 FEATURES_PROVIDED += periph_gpio_ll_switch_dir
+FEATURES_PROVIDED += periph_gpio
+FEATURES_PROVIDED += periph_gpio_irq
 FEATURES_PROVIDED += periph_pm
 FEATURES_PROVIDED += periph_rtc_ms
 FEATURES_PROVIDED += periph_rtt_overflow

@@ -6,6 +6,7 @@ FEATURES_PROVIDED += cpp
 FEATURES_PROVIDED += cpu_check_address
 FEATURES_PROVIDED += cpu_core_cortexm
 FEATURES_PROVIDED += dbgpin
+FEATURES_PROVIDED += float_math
 FEATURES_PROVIDED += libstdcpp
 FEATURES_PROVIDED += newlib
 FEATURES_PROVIDED += periph_flashpage_aux

@@ -4,6 +4,7 @@ FEATURES_PROVIDED += arch_32bit
 FEATURES_PROVIDED += arch_esp
 FEATURES_PROVIDED += cpp
 FEATURES_PROVIDED += esp_spiffs
+FEATURES_PROVIDED += float_math
 FEATURES_PROVIDED += libstdcpp
 FEATURES_PROVIDED += newlib
 FEATURES_PROVIDED += periph_cpuid

@@ -17,13 +17,13 @@ FEATURES_PROVIDED += arch_msp430
 FEATURES_PROVIDED += bug_newlib_broken_stdio
 FEATURES_PROVIDED += cpu_$(CPU_FAM)
 FEATURES_PROVIDED += dbgpin
+FEATURES_PROVIDED += float_math
 FEATURES_PROVIDED += newlib
 FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_flashpage_in_address_space
 FEATURES_PROVIDED += periph_flashpage_pagewise
-FEATURES_PROVIDED += periph_pm
-FEATURES_PROVIDED += periph_timer_query_freqs
-
 FEATURES_PROVIDED += periph_gpio_ll
 FEATURES_PROVIDED += periph_gpio_ll_irq
 FEATURES_PROVIDED += periph_gpio_ll_switch_dir
+FEATURES_PROVIDED += periph_pm
+FEATURES_PROVIDED += periph_timer_query_freqs
diff --git a/cpu/native/Makefile.include b/cpu/native/Makefile.include
@@ -37,3 +37,22 @@ ifeq ($(USE_LIBUCONTEXT),1)
   CFLAGS += $(pkg-config libucontext --cflags) -DUSE_LIBUCONTEXT=1
   LINKFLAGS += $(shell pkg-config libucontext --libs)
 endif
+
+ifeq (x86_64,$(OS_ARCH))
+  # Disable use of FPU/SSE registers if FPU is not used. This prevents radom
+  # stack corruptions and floating point exceptions to not occur during
+  # context switching.
+	ifeq (,$(filter float_math,$(FEATURES_USED)))
+		# FPU/SSE registers are not reliably saved and restored in glibc's ucontext
+		# implementation (see https://github.com/RIOT-OS/RIOT/issues/495) and not at
+		# all in libucontext's (but there at least this is documented). So we force
+		# the compiler to only use registers known to be properly backed up and
+		# restored during context switching
+		CFLAGS += -mgeneral-regs-only
+
+		# Since we disabled the use of non-general registers (such as FPU registers),
+		# we need to use a soft FPU
+		CFLAGS += -msoft-float
+		LINKFLAGS += -msoft-float
+	endif
+endif
diff --git a/cpu/riscv_common/Makefile.features b/cpu/riscv_common/Makefile.features
@@ -6,6 +6,7 @@ FEATURES_PROVIDED += arch_32bit
 FEATURES_PROVIDED += arch_riscv
 FEATURES_PROVIDED += bug_newlib_broken_stdio
 FEATURES_PROVIDED += cpp
+FEATURES_PROVIDED += float_math
 FEATURES_PROVIDED += libstdcpp
 FEATURES_PROVIDED += newlib
 FEATURES_PROVIDED += periph_coretimer

diff --git a/drivers/adt7310/Makefile.dep b/drivers/adt7310/Makefile.dep
@@ -1 +1,2 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_spi
diff --git a/drivers/apds99xx/Makefile.dep b/drivers/apds99xx/Makefile.dep
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_i2c
 
 ifneq (,$(filter apds99%full,$(USEMODULE)))

diff --git a/drivers/at30tse75x/Makefile.dep b/drivers/at30tse75x/Makefile.dep
@@ -1,2 +1,4 @@
-USEMODULE += ztimer_usec
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_i2c
+
+USEMODULE += ztimer_usec
diff --git a/drivers/bme680/Makefile.dep b/drivers/bme680/Makefile.dep
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 USEPKG += driver_bme680
 
 ifneq (,$(filter saul%,$(USEMODULE)))

diff --git a/drivers/bmp180/Makefile.dep b/drivers/bmp180/Makefile.dep
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_i2c
 USEMODULE += ztimer
 USEMODULE += ztimer_msec
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_gpio
 FEATURES_REQUIRED += periph_i2c
 USEMODULE += ztimer

diff --git a/drivers/io1_xplained/Makefile.dep b/drivers/io1_xplained/Makefile.dep
@@ -1,4 +1,6 @@
-FEATURES_REQUIRED += periph_gpio
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_adc
+FEATURES_REQUIRED += periph_gpio
+
 USEMODULE += at30tse75x
 USEMODULE += sdcard_spi
diff --git a/drivers/isl29125/Makefile.dep b/drivers/isl29125/Makefile.dep
@@ -1,2 +1,3 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_gpio_irq
 FEATURES_REQUIRED += periph_i2c
diff --git a/drivers/kw41zrf/Makefile.dep b/drivers/kw41zrf/Makefile.dep
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 USEMODULE += ieee802154
 USEMODULE += netdev_ieee802154
 USEMODULE += netdev_legacy_api

diff --git a/drivers/scd30/Makefile.dep b/drivers/scd30/Makefile.dep
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_i2c
 USEMODULE += checksum
 USEMODULE += xtimer
diff --git a/drivers/sps30/Makefile.dep b/drivers/sps30/Makefile.dep
@@ -1,2 +1,3 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_i2c
 USEMODULE += checksum
@@ -1,3 +1,4 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_gpio
 FEATURES_REQUIRED += periph_gpio_irq
 FEATURES_REQUIRED += periph_spi

diff --git a/drivers/sx1280/Makefile.dep b/drivers/sx1280/Makefile.dep
@@ -1,3 +1,6 @@
+FEATURES_REQUIRED += float_math
+
 USEPKG += lorabasics
+
 USEMODULE += lorabasics_sx1280_driver
 USEMODULE += netdev_legacy_api
diff --git a/drivers/tmp00x/Makefile.dep b/drivers/tmp00x/Makefile.dep
@@ -1,2 +1,3 @@
+FEATURES_REQUIRED += float_math
 FEATURES_REQUIRED += periph_i2c
 USEMODULE += xtimer
diff --git a/examples/lang_support/official/riot_and_cpp/Makefile b/examples/lang_support/official/riot_and_cpp/Makefile
@@ -27,6 +27,8 @@ DEVELHELP ?= 1
 # Change this to 0 show compiler invocation lines by default:
 QUIET ?= 1
 
+USEMODULE += printf_float
+
 # Features required
 FEATURES_REQUIRED += cpp # basic C++ support
 FEATURES_REQUIRED += libstdcpp # libstdc++ support (for #include <cstdio>)

diff --git a/examples/networking/misc/spectrum-scanner/Makefile b/examples/networking/misc/spectrum-scanner/Makefile
@@ -7,6 +7,9 @@ BOARD ?= samr21-xpro
 # This has to be the absolute path to the RIOT base directory:
 RIOTBASE ?= $(CURDIR)/../../../..
 
+# Needed for print_float()
+FEATURES_REQUIRED += float_math
+
 # Define modules that are used
 USEMODULE += gnrc
 USEMODULE += netdev_default

diff --git a/features.yaml b/features.yaml
@@ -468,6 +468,9 @@ groups:
           a mandatory requirement to build Rust code.
   - name: emulator_renode
     help: The platform is compatible with the Renode emulator.
+  - name: float_math
+    help: The use of float point math is possible. This requires either a
+          hardware FPU or a working software FPU.
 
 - title: Peripheral Features
   help: These features indicate presence of peripheral IP block, presence of

diff --git a/makefiles/features_existing.inc.mk b/makefiles/features_existing.inc.mk
@@ -129,6 +129,7 @@ FEATURES_EXISTING := \
     esp_wifi_ap \
     esp_wifi_enterprise \
     feather_shield \
+    float_math \
     gecko_sdk_librail_fpu \
     gecko_sdk_librail_nonfpu \
     highlevel_stdio \

diff --git a/makefiles/features_modules.inc.mk b/makefiles/features_modules.inc.mk
@@ -124,6 +124,9 @@ USEMODULE += $(filter vdd_lc_filter_%,$(FEATURES_USED))
 # select arduino_pwm pseudomodule if the corresponding feature is used
 USEMODULE += $(filter arduino_pwm, $(FEATURES_USED))
 
+# select float_math pseudomodule when corresponding feature is used
+USEMODULE += $(filter float_math, $(FEATURES_USED))
+
 # always register a peripheral driver as a required feature when the corresponding
 # module is requested
 PERIPH_IGNORE_MODULES += periph_usbdev_clk periph_gpio_mock periph_gpio_linux periph_spidev_linux

diff --git a/makefiles/pseudomodules.inc.mk b/makefiles/pseudomodules.inc.mk
@@ -79,6 +79,7 @@ PSEUDOMODULES += event_timeout_ztimer
 PSEUDOMODULES += evtimer_mbox
 PSEUDOMODULES += fatfs_vfs_format
 PSEUDOMODULES += fdcan
+PSEUDOMODULES += float_math
 PSEUDOMODULES += fmt_%
 PSEUDOMODULES += gcoap_forward_proxy
 PSEUDOMODULES += gcoap_forward_proxy_thread

diff --git a/pkg/cayenne-lpp/Makefile.dep b/pkg/cayenne-lpp/Makefile.dep
@@ -0,0 +1 @@
+FEATURES_REQUIRED += float_math
diff --git a/pkg/ccn-lite/Makefile.dep b/pkg/ccn-lite/Makefile.dep
@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 USEMODULE += ccn-lite-utils
 USEMODULE += gnrc_nettype_ccn
 USEMODULE += evtimer

diff --git a/pkg/cn-cbor/Makefile.dep b/pkg/cn-cbor/Makefile.dep
@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 USEMODULE += posix_headers
 
 # CN-CBOR is only supported by 32 bit architectures

diff --git a/pkg/emlearn/Makefile.dep b/pkg/emlearn/Makefile.dep
@@ -1,2 +1,4 @@
+FEATURES_REQUIRED += float_math
+
 # emlearn is not compatible with MSP430
 FEATURES_BLACKLIST += arch_msp430
diff --git a/pkg/flatbuffers/Makefile.dep b/pkg/flatbuffers/Makefile.dep
@@ -1 +1,3 @@
+FEATURES_REQUIRED += float_math
+
 USEMODULE += cpp11-compat
diff --git a/pkg/jerryscript/Makefile.dep b/pkg/jerryscript/Makefile.dep
@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 USEMODULE += jerryscript-port-default
 USEMODULE += jerryscript-ext
 

diff --git a/pkg/libfixmath/Makefile.dep b/pkg/libfixmath/Makefile.dep
@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 ifneq (,$(filter libfixmath-unittests,$(USEMODULE)))
   # libfixmath unittests use shift operand incompatible with 8bit
   # architecture int type.

@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 ifneq (,$(filter libschc_%,$(USEMODULE)))
   USEPKG += libschc
 endif

@@ -0,0 +1 @@
+FEATURES_REQUIRED += float_math
diff --git a/pkg/lvgl/Makefile.dep b/pkg/lvgl/Makefile.dep
@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 USEMODULE += lvgl
 USEMODULE += lvgl_core
 USEMODULE += lvgl_draw

@@ -1,3 +1,5 @@
+FEATURES_REQUIRED += float_math
+
 USEMODULE += xtimer
 USEMODULE += stdin
 

diff --git a/pkg/minmea/Makefile.dep b/pkg/minmea/Makefile.dep
@@ -0,0 +1 @@
+FEATURES_REQUIRED += float_math
diff --git a/pkg/mjson/Makefile.dep b/pkg/mjson/Makefile.dep
@@ -0,0 +1 @@
+FEATURES_REQUIRED += float_math
diff --git a/pkg/nanocbor/Makefile.dep b/pkg/nanocbor/Makefile.dep
@@ -0,0 +1 @@
+FEATURES_OPTIONAL += float_math
diff --git a/pkg/nanocbor/Makefile.include b/pkg/nanocbor/Makefile.include
@@ -1,2 +1,7 @@
 INCLUDES += -I$(RIOTPKG)/nanocbor/include
 INCLUDES += -I$(PKGDIRBASE)/nanocbor/include
+
+# Disable float functions if no float support is available
+ifneq (,$(filter float_math,$(FEATURES_USED)))
+  CFLAGS += -DNANOCBOR_ENABLE_FLOAT=0
+endif
diff --git a/pkg/nanocbor/patches/0001-config-Allow-disabling-of-float-arithmitc.patch b/pkg/nanocbor/patches/0001-config-Allow-disabling-of-float-arithmitc.patch
@@ -0,0 +1,109 @@
+From e29136bb10b7d763d633341e213112759c6893a0 Mon Sep 17 00:00:00 2001
+From: Marian Buschsieweke <marian.buschsieweke@ml-pa.com>
+Date: Wed, 17 Sep 2025 21:36:01 +0200
+Subject: [PATCH] config: Allow disabling of float arithmitc
+
+This can be useful for toolchains that cannot compile with any float
+arithmetic included. Otherwise with -ffunction-sections the linker would
+garbage collect unused float support anyway.
+---
+ examples/pretty-printer/main.c | 4 ++++
+ include/nanocbor/config.h      | 7 +++++++
+ src/decoder.c                  | 2 ++
+ src/encoder.c                  | 3 +++
+ 4 files changed, 16 insertions(+)
+
+diff --git a/examples/pretty-printer/main.c b/examples/pretty-printer/main.c
+index 9508ecf..1811f0a 100644
+--- a/examples/pretty-printer/main.c
++++ b/examples/pretty-printer/main.c
+@@ -144,6 +144,7 @@ static int _print_enter_array(nanocbor_value_t *value, unsigned indent)
+     return -1;
+ }
+
++#if NANOCBOR_ENABLE_FLOAT
+ static int _print_float(nanocbor_value_t *value)
+ {
+     bool test = false;
+@@ -173,6 +174,7 @@ static int _print_float(nanocbor_value_t *value)
+     }
+     return 0;
+ }
++#endif /* NANOCBOR_ENABLE_FLOAT */
+
+ /* NOLINTNEXTLINE(misc-no-recursion, readability-function-cognitive-complexity) */
+ static int _parse_type(nanocbor_value_t *value, unsigned indent)
+@@ -228,9 +230,11 @@ static int _parse_type(nanocbor_value_t *value, unsigned indent)
+     case NANOCBOR_TYPE_MAP: {
+         res = _print_enter_map(value, indent);
+     } break;
++#if NANOCBOR_ENABLE_FLOAT
+     case NANOCBOR_TYPE_FLOAT: {
+         res = _print_float(value);
+     } break;
++#endif /* NANOCBOR_ENABLE_FLOAT */
+     case NANOCBOR_TYPE_TAG: {
+         uint32_t tag = 0;
+         int res = nanocbor_get_tag(value, &tag);
+diff --git a/include/nanocbor/config.h b/include/nanocbor/config.h
+index a9e5463..bf4e135 100644
+--- a/include/nanocbor/config.h
++++ b/include/nanocbor/config.h
+@@ -79,6 +79,13 @@ extern "C" {
+ #endif
+ #endif
+
++/**
++ * @brief enable/disable support for float/double values
++ */
++#ifndef NANOCBOR_ENABLE_FLOAT
++#define NANOCBOR_ENABLE_FLOAT 1
++#endif
++
+ #ifdef __cplusplus
+ }
+ #endif
+diff --git a/src/decoder.c b/src/decoder.c
+index 5820659..4a59e01 100644
+--- a/src/decoder.c
++++ b/src/decoder.c
+@@ -368,6 +368,7 @@ int nanocbor_get_simple(nanocbor_value_t *cvalue, uint8_t *value)
+     return res;
+ }
+
++#if NANOCBOR_ENABLE_FLOAT
+ /* float bit mask related defines */
+ #define FLOAT_EXP_OFFSET (127U)
+ #define FLOAT_SIZE (32U)
+@@ -475,6 +476,7 @@ int nanocbor_get_double(nanocbor_value_t *cvalue, double *value)
+     }
+     return _decode_double(cvalue, value);
+ }
++#endif /* NANOCBOR_ENABLE_FLOAT */
+
+ static int _enter_container(const nanocbor_value_t *it,
+                             nanocbor_value_t *container, uint8_t type)
+diff --git a/src/encoder.c b/src/encoder.c
+index ec0a4f6..c548fbd 100644
+--- a/src/encoder.c
++++ b/src/encoder.c
+@@ -230,6 +230,8 @@ int nanocbor_fmt_null(nanocbor_encoder_t *enc)
+     return _fmt_single(enc, NANOCBOR_MASK_FLOAT | NANOCBOR_SIMPLE_NULL);
+ }
+
++#if NANOCBOR_TYPE_FLOAT
++
+ /* Double bit mask related defines */
+ #define DOUBLE_EXP_OFFSET (1023U)
+ #define DOUBLE_SIZE (64U)
+@@ -393,6 +395,7 @@ int nanocbor_fmt_double(nanocbor_encoder_t *enc, double num)
+     return res;
+ #endif
+ }
++#endif /* NANOCBOR_TYPE_FLOAT */
+
+ int nanocbor_fmt_decimal_frac(nanocbor_encoder_t *enc, int32_t e, int32_t m)
+ {
+-- 
+2.43.0
+
Original file line number	Diff line number	Diff line change
		@@ -1 +1,2 @@
		FEATURES_REQUIRED += float_math
		FEATURES_REQUIRED += periph_spi
Original file line number	Diff line number	Diff line change
		@@ -1 +1,3 @@
		FEATURES_REQUIRED += float_math

		USEMODULE += cpp11-compat