cgo: add support for printf

The C printf function is sometimes needed for C files included using
CGo. This commit makes sure they're available on all systems where CGo
is fully supported (that is, everywhere except on AVR).

For baremetal systems using picolibc, I've picked the integer-only
version of printf to save on flash size. We might want to consider
providing a way to pick the floating point version instead, if needed.

9 files changed, 45 insertions, 7 deletions

diff --git a/GNUmakefile b/GNUmakefile
index d560ae82e..986d51940 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -856,6 +856,7 @@ build/release: tinygo gen-device wasi-libc $(if $(filter 1,$(USE_SYSTEM_BINARYEN
 	@mkdir -p build/release/tinygo/lib/CMSIS/CMSIS
 	@mkdir -p build/release/tinygo/lib/macos-minimal-sdk
 	@mkdir -p build/release/tinygo/lib/mingw-w64/mingw-w64-crt/lib-common
+	@mkdir -p build/release/tinygo/lib/mingw-w64/mingw-w64-crt/stdio
 	@mkdir -p build/release/tinygo/lib/mingw-w64/mingw-w64-headers/defaults
 	@mkdir -p build/release/tinygo/lib/musl/arch
 	@mkdir -p build/release/tinygo/lib/musl/crt
@@ -891,10 +892,12 @@ endif
 	@cp -rp lib/musl/src/include         build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/internal        build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/legacy          build/release/tinygo/lib/musl/src
+	@cp -rp lib/musl/src/locale          build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/linux           build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/malloc          build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/mman            build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/math            build/release/tinygo/lib/musl/src
+	@cp -rp lib/musl/src/multibyte       build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/signal          build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/stdio           build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/string          build/release/tinygo/lib/musl/src
@@ -904,6 +907,7 @@ endif
 	@cp -rp lib/mingw-w64/mingw-w64-crt/def-include                 build/release/tinygo/lib/mingw-w64/mingw-w64-crt
 	@cp -rp lib/mingw-w64/mingw-w64-crt/lib-common/api-ms-win-crt-* build/release/tinygo/lib/mingw-w64/mingw-w64-crt/lib-common
 	@cp -rp lib/mingw-w64/mingw-w64-crt/lib-common/kernel32.def.in  build/release/tinygo/lib/mingw-w64/mingw-w64-crt/lib-common
+	@cp -rp lib/mingw-w64/mingw-w64-crt/stdio/ucrt_*                build/release/tinygo/lib/mingw-w64/mingw-w64-crt/stdio
 	@cp -rp lib/mingw-w64/mingw-w64-headers/crt/                    build/release/tinygo/lib/mingw-w64/mingw-w64-headers
 	@cp -rp lib/mingw-w64/mingw-w64-headers/defaults/include        build/release/tinygo/lib/mingw-w64/mingw-w64-headers/defaults
 	@cp -rp lib/nrfx/*                   build/release/tinygo/lib/nrfx
diff --git a/builder/build.go b/builder/build.go
index 54f5c101b..d16bf170b 100644
--- a/builder/build.go
+++ b/builder/build.go
@@ -176,11 +176,12 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 		defer unlock()
 		libcDependencies = append(libcDependencies, libcJob)
 	case "mingw-w64":
-		_, unlock, err := libMinGW.load(config, tmpdir)
+		job, unlock, err := libMinGW.load(config, tmpdir)
 		if err != nil {
 			return BuildResult{}, err
 		}
-		unlock()
+		defer unlock()
+		libcDependencies = append(libcDependencies, job)
 		libcDependencies = append(libcDependencies, makeMinGWExtraLibs(tmpdir, config.GOARCH())...)
 	case "":
 		// no library specified, so nothing to do
diff --git a/builder/mingw-w64.go b/builder/mingw-w64.go
index 6b0c966fa..32cf58f53 100644
--- a/builder/mingw-w64.go
+++ b/builder/mingw-w64.go
@@ -27,14 +27,30 @@ var libMinGW = Library{
 		_, err = io.Copy(outf, inf)
 		return err
 	},
-	sourceDir: func() string { return "" }, // unused
+	sourceDir: func() string { return filepath.Join(goenv.Get("TINYGOROOT"), "lib/mingw-w64") },
 	cflags: func(target, headerPath string) []string {
-		// No flags necessary because there are no files to compile.
-		return nil
+		mingwDir := filepath.Join(goenv.Get("TINYGOROOT"), "lib/mingw-w64")
+		return []string{
+			"-nostdlibinc",
+			"-isystem", mingwDir + "/mingw-w64-headers/crt",
+			"-I", mingwDir + "/mingw-w64-headers/defaults/include",
+			"-I" + headerPath,
+		}
 	},
 	librarySources: func(target string) ([]string, error) {
-		// We only use the UCRT DLL file. No source files necessary.
-		return nil, nil
+		// These files are needed so that printf and the like are supported.
+		sources := []string{
+			"mingw-w64-crt/stdio/ucrt_fprintf.c",
+			"mingw-w64-crt/stdio/ucrt_fwprintf.c",
+			"mingw-w64-crt/stdio/ucrt_printf.c",
+			"mingw-w64-crt/stdio/ucrt_snprintf.c",
+			"mingw-w64-crt/stdio/ucrt_sprintf.c",
+			"mingw-w64-crt/stdio/ucrt_vfprintf.c",
+			"mingw-w64-crt/stdio/ucrt_vprintf.c",
+			"mingw-w64-crt/stdio/ucrt_vsnprintf.c",
+			"mingw-w64-crt/stdio/ucrt_vsprintf.c",
+		}
+		return sources, nil
 	},
 }
 
diff --git a/builder/musl.go b/builder/musl.go
index 87253fce1..8130981e6 100644
--- a/builder/musl.go
+++ b/builder/musl.go
@@ -92,6 +92,8 @@ var libMusl = Library{
 			"-Wno-ignored-pragmas",
 			"-Wno-tautological-constant-out-of-range-compare",
 			"-Wno-deprecated-non-prototype",
+			"-Wno-format",
+			"-Wno-parentheses",
 			"-Qunused-arguments",
 			// Select include dirs. Don't include standard library includes
 			// (that would introduce host dependencies and other complications),
@@ -119,11 +121,13 @@ var libMusl = Library{
 			"internal/syscall_ret.c",
 			"internal/vdso.c",
 			"legacy/*.c",
+			"locale/*.c",
 			"linux/*.c",
 			"malloc/*.c",
 			"malloc/mallocng/*.c",
 			"mman/*.c",
 			"math/*.c",
+			"multibyte/*.c",
 			"signal/*.c",
 			"stdio/*.c",
 			"string/*.c",
diff --git a/builder/picolibc.go b/builder/picolibc.go
index 82b3c5319..d33f31c09 100644
--- a/builder/picolibc.go
+++ b/builder/picolibc.go
@@ -29,6 +29,7 @@ var libPicolibc = Library{
 			"-D_HAVE_ALIAS_ATTRIBUTE",
 			"-DTINY_STDIO",
 			"-DPOSIX_IO",
+			"-DFORMAT_DEFAULT_INTEGER", // use __i_vfprintf and __i_vfscanf by default
 			"-D_IEEE_LIBM",
 			"-D__OBSOLETE_MATH_FLOAT=1", // use old math code that doesn't expect a FPU
 			"-D__OBSOLETE_MATH_DOUBLE=0",
diff --git a/testdata/cgo/main.c b/testdata/cgo/main.c
index 7fb702ed6..4a5bd6b9c 100644
--- a/testdata/cgo/main.c
+++ b/testdata/cgo/main.c
@@ -1,5 +1,6 @@
 #include <math.h>
 #include "main.h"
+#include <stdio.h>
 
 int global = 3;
 bool globalBool = 1;
@@ -72,3 +73,7 @@ void arraydecay(int buf1[5], int buf2[3][8], int buf3[4][7][2]) {
 double doSqrt(double x) {
 	return sqrt(x);
 }
+
+void printf_single_int(char *format, int arg) {
+	printf(format, arg);
+}
diff --git a/testdata/cgo/main.go b/testdata/cgo/main.go
index fa3380bce..ddd1992e2 100644
--- a/testdata/cgo/main.go
+++ b/testdata/cgo/main.go
@@ -179,6 +179,10 @@ func main() {
 	// libc: test basic stdio functionality
 	putsBuf := []byte("line written using C puts\x00")
 	C.puts((*C.char)(unsafe.Pointer(&putsBuf[0])))
+
+	// libc: test whether printf works in C.
+	printfBuf := []byte("line written using C printf with value=%d\n\x00")
+	C.printf_single_int((*C.char)(unsafe.Pointer(&printfBuf[0])), -21)
 }
 
 func printUnion(union C.joined_t) C.joined_t {
diff --git a/testdata/cgo/main.h b/testdata/cgo/main.h
index f5405ade6..e7c64ffc3 100644
--- a/testdata/cgo/main.h
+++ b/testdata/cgo/main.h
@@ -152,3 +152,5 @@ typedef int arraydecay_buf3[4][7][2];
 void arraydecay(int buf1[5], int buf2[3][8], arraydecay_buf3 buf3);
 
 double doSqrt(double);
+
+void printf_single_int(char *format, int arg);
diff --git a/testdata/cgo/out.txt b/testdata/cgo/out.txt
index ae92c87a7..4ea45d864 100644
--- a/testdata/cgo/out.txt
+++ b/testdata/cgo/out.txt
@@ -77,3 +77,4 @@ copied string: foobar
 CGo sqrt(3): +1.732051e+000
 C   sqrt(3): +1.732051e+000
 line written using C puts
+line written using C printf with value=-21