all: use -Qunused-arguments only for assembly files

The -Qunused-arguments flag disables the warning where some flags are
not relevant to a compilation. This commonly happens when compiling
assembly files (.s or .S files) because some flags are specific to C and
not relevant to assembly.
Because practically all baremetal targets need some form of assembly,
this flag is added to most CFlags. This creates a lot of noise. And it
is also added for compiling C code where it might hide bugs (by hiding
the fact a flag is actually unused).

This commit adds the flag to all assembly compilations and removes them
from all target JSON files.

builder/cc.go

@@ -124,6 +124,13 @@ func compileAndCacheCFile(abspath, tmpdir string, cflags []string, config *compi
 	flags := append([]string{}, cflags...)                                   // copy cflags
 	flags = append(flags, "-MD", "-MV", "-MTdeps", "-MF", depTmpFile.Name()) // autogenerate dependencies
 	flags = append(flags, "-c", "-o", objTmpFile.Name(), abspath)
+	if strings.ToLower(filepath.Ext(abspath)) == ".s" {
+		// If this is an assembly file (.s or .S, lowercase or uppercase), then
+		// we'll need to add -Qunused-arguments because many parameters are
+		// relevant to C, not assembly. And with -Werror, having meaningless
+		// flags (for the assembler) is a compiler error.
+		flags = append(flags, "-Qunused-arguments")
+	}
 	if config.Options.PrintCommands {
 		fmt.Printf("%s %s\n", config.Target.Compiler, strings.Join(flags, " "))
 	}

targets/atsamd21e18a.json

@@ -3,8 +3,7 @@
 	"llvm-target": "armv6m-none-eabi",
 	"build-tags": ["atsamd21e18a", "atsamd21e18", "atsamd21", "sam"],
 	"cflags": [
-		"--target=armv6m-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv6m-none-eabi"
 	],
 	"linkerscript": "targets/atsamd21.ld",
 	"extra-files": [

targets/atsamd21g18a.json

@@ -3,8 +3,7 @@
 	"llvm-target": "armv6m-none-eabi",
 	"build-tags": ["atsamd21g18a", "atsamd21g18", "atsamd21", "sam"],
 	"cflags": [
-		"--target=armv6m-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv6m-none-eabi"
 	],
 	"linkerscript": "targets/atsamd21.ld",
 	"extra-files": [

targets/atsamd51g19a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["atsamd51g19a", "atsamd51g19", "atsamd51", "sam"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51g19a.s"

targets/atsamd51j19a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["atsamd51j19a", "atsamd51j19", "atsamd51", "sam"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51j19a.s"

targets/atsamd51j20a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["sam", "atsamd51", "atsamd51j20", "atsamd51j20a"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51j20a.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51j20a.s"

targets/atsamd51p19a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["atsamd51p19a", "atsamd51p19", "atsamd51", "sam"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51p19a.s"

targets/atsamd51p20a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["sam", "atsamd51", "atsamd51p20", "atsamd51p20a"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51p20a.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51p20a.s"

targets/attiny85.json

@@ -4,8 +4,7 @@
 	"build-tags": ["attiny85", "attiny", "avr2", "avr25"],
 	"cflags": [
 		"-mmcu=attiny85",
-		"-D__AVR_ARCH__=25",
-		"-Qunused-arguments"
+		"-D__AVR_ARCH__=25"
 	],
 	"ldflags": [
 		"-mmcu=avr25"

targets/avr.json

@@ -9,7 +9,8 @@
 	"scheduler": "none",
 	"default-stack-size": 256,
 	"cflags": [
-		"--target=avr-unknown-unknown"
+		"--target=avr-unknown-unknown",
+		"-Werror"
 	],
 	"ldflags": [
 		"-T", "targets/avr.ld",

targets/bluepill.json

@@ -3,8 +3,7 @@
 	"llvm-target": "armv7m-none-eabi",
 	"build-tags": ["bluepill", "stm32f103", "stm32f1", "stm32"],
 	"cflags": [
-		"--target=armv7m-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv7m-none-eabi"
 	],
 	"linkerscript": "targets/stm32.ld",
 	"extra-files": [

targets/cortex-m-qemu.json

@@ -3,8 +3,7 @@
 	"llvm-target": "armv7m-none-eabi",
 	"build-tags": ["qemu", "lm3s6965"],
 	"cflags": [
-		"--target=armv7m-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv7m-none-eabi"
 	],
 	"linkerscript": "targets/lm3s6965.ld",
 	"extra-files": [

targets/cortex-m0.json

@@ -2,7 +2,6 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv6m-none-eabi",
 	"cflags": [
-		"--target=armv6m-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv6m-none-eabi"
 	]
 }

targets/cortex-m33.json

@@ -3,7 +3,6 @@
     "llvm-target": "armv7m-none-eabi",
     "cflags": [
         "--target=armv7m-none-eabi",
-        "-mfloat-abi=soft",
-        "-Qunused-arguments"
+        "-mfloat-abi=soft"
     ]
 }

targets/cortex-m4.json

@@ -3,7 +3,6 @@
 	"llvm-target": "armv7em-none-eabi",
 	"cflags": [
 		"--target=armv7em-none-eabi",
-		"-mfloat-abi=soft",
-		"-Qunused-arguments"
+		"-mfloat-abi=soft"
 	]
 }

targets/cortex-m7.json

@@ -2,7 +2,6 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv7em-none-eabi",
 	"cflags": [
-		"--target=armv7em-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv7em-none-eabi"
 	]
 }

targets/feather-stm32f405.json

@@ -3,9 +3,6 @@
   "build-tags": ["feather_stm32f405", "stm32f405", "stm32f4", "stm32"],
   "automatic-stack-size": false,
   "default-stack-size": 1024,
-  "cflags": [
-    "-Qunused-arguments"
-  ],
   "linkerscript": "targets/stm32f405.ld",
   "extra-files": [
     "src/device/stm32/stm32f405.s"

targets/gameboy-advance.json

@@ -15,7 +15,6 @@
 		"-Werror",
 		"-fshort-enums",
 		"-fomit-frame-pointer",
-		"-Qunused-arguments",
 		"-fno-exceptions", "-fno-unwind-tables",
 		"-ffunction-sections", "-fdata-sections"
 	],

targets/nintendoswitch.json

@@ -15,7 +15,6 @@
     "-mcpu=cortex-a57",
     "-fPIE",
     "-Werror",
-    "-Qunused-arguments",
     "-fshort-enums",
     "-fomit-frame-pointer",
     "-fno-exceptions", "-fno-unwind-tables",

targets/nrf51.json

@@ -4,7 +4,6 @@
 	"build-tags": ["nrf51822", "nrf51", "nrf"],
 	"cflags": [
 		"--target=armv6m-none-eabi",
-		"-Qunused-arguments",
 		"-DNRF51",
 		"-I{root}/lib/CMSIS/CMSIS/Include",
 		"-I{root}/lib/nrfx/mdk"

targets/nrf52.json

@@ -2,7 +2,6 @@
 	"inherits": ["cortex-m4"],
 	"build-tags": ["nrf52", "nrf"],
 	"cflags": [
-		"-Qunused-arguments",
 		"-DNRF52832_XXAA",
 		"-I{root}/lib/CMSIS/CMSIS/Include",
 		"-I{root}/lib/nrfx/mdk"

targets/nrf52833.json

@@ -2,7 +2,6 @@
 	"inherits": ["cortex-m4"],
 	"build-tags": ["nrf52833", "nrf"],
 	"cflags": [
-		"-Qunused-arguments",
 		"-DNRF52833_XXAA",
 		"-I{root}/lib/CMSIS/CMSIS/Include",
 		"-I{root}/lib/nrfx/mdk"

targets/nrf52840.json

@@ -2,7 +2,6 @@
 	"inherits": ["cortex-m4"],
 	"build-tags": ["nrf52840", "nrf"],
 	"cflags": [
-		"-Qunused-arguments",
 		"-DNRF52840_XXAA",
 		"-I{root}/lib/CMSIS/CMSIS/Include",
 		"-I{root}/lib/nrfx/mdk"

targets/nucleo-f103rb.json

@@ -3,8 +3,7 @@
   "llvm-target": "armv7m-none-eabi",
   "build-tags": ["nucleof103rb", "stm32f103", "stm32f1","stm32"],
   "cflags": [
-    "--target=armv7m-none-eabi",
-    "-Qunused-arguments"
+    "--target=armv7m-none-eabi"
   ],
   "linkerscript": "targets/stm32f103rb.ld",
   "extra-files": [

targets/stm32f4disco.json

@@ -1,9 +1,6 @@
 {
   "inherits": ["cortex-m4"],
   "build-tags": ["stm32f4disco", "stm32f407", "stm32f4", "stm32"],
-  "cflags": [
-    "-Qunused-arguments"
-  ],
   "linkerscript": "targets/stm32f407.ld",
   "extra-files": [
     "src/device/stm32/stm32f407.s"

targets/stm32l0x2.json

@@ -9,8 +9,7 @@
         "stm32"
     ],
     "cflags": [
-        "--target=armv6m-none-eabi",
-        "-Qunused-arguments"
+        "--target=armv6m-none-eabi"
     ],
     "extra-files": [
         "src/device/stm32/stm32l0x2.s"

targets/teensy36.json

@@ -5,7 +5,6 @@
 	"build-tags": ["teensy36", "teensy", "mk66f18", "nxp"],
 	"cflags": [
 		"--target=armv7em-none-eabi",
-		"-Qunused-arguments",
 		"-mfloat-abi=hard",
 		"-mfpu=fpv4-sp-d16"
 	],

targets/teensy40.json

@@ -7,7 +7,6 @@
   "default-stack-size": 4096,
   "cflags": [
     "--target=armv7em-none-eabi",
-    "-Qunused-arguments",
     "-mfloat-abi=soft"
   ],
   "linkerscript": "targets/mimxrt1062-teensy40.ld",

targets/xtensa.json

@@ -12,7 +12,6 @@
 		"-Werror",
 		"-fshort-enums",
 		"-Wno-macro-redefined",
-		"-Qunused-arguments",
 		"-fno-exceptions", "-fno-unwind-tables",
 		"-ffunction-sections", "-fdata-sections"
 	],