mbed-retarget: Make filehandles optional to reduce code size

The retarget code allocates an array of FileHandle* for console and file
handling (filehandles). A tiny target only needs a console (putc/getc).
There is no need for file handling.
The POSIX layer and the array of FileHandle* is not required for small
targets that only need a console ; this code should be optionally compiled
out if the configuration parameter `platform.stdio-console-only` is
selected instead of `platform-stdio-buffered-serial`.

Author: hugueskamba

platform/mbed_lib.json

@@ -16,6 +16,11 @@
             "value": false
         },
 
+        "stdio-console-only": {
+            "help": "(Applies if target.console-uart is true.) Enable this instead of `stdio-buffered-serial` if filehandles are not required to access the serial interface as console to only to print.",
+            "value": false
+        },
+
         "stdio-baud-rate": {
             "help": "(Applies if target.console-uart is true.) Baud rate for stdio",
             "value": 9600

platform/source/mbed_retarget.cpp

@@ -30,6 +30,7 @@
 #include "platform/mbed_critical.h"
 #include "platform/mbed_poll.h"
 #include "drivers/UARTSerial.h"
+#include "drivers/RawSerial.h"
 #include "hal/us_ticker_api.h"
 #include "hal/lp_ticker_api.h"
 #include <stdlib.h>
@@ -104,6 +105,7 @@ extern const char __stderr_name[] = "/stderr";
 unsigned char *mbed_heap_start = 0;
 uint32_t mbed_heap_size = 0;
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 /* newlib has the filehandle field in the FILE struct as a short, so
  * we can't just return a Filehandle* from _open and instead have to
  * put it in a filehandles array and return the index into that array
@@ -112,12 +114,14 @@ static FileHandle *filehandles[OPEN_MAX] = { FILE_HANDLE_RESERVED, FILE_HANDLE_R
 static char stdio_in_prev[OPEN_MAX];
 static char stdio_out_prev[OPEN_MAX];
 static SingletonPtr<PlatformMutex> filehandle_mutex;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 namespace mbed {
 void mbed_set_unbuffered_stream(std::FILE *_file);
 
 void remove_filehandle(FileHandle *file)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     filehandle_mutex->lock();
     /* Remove all open filehandles for this */
     for (unsigned int fh_i = 0; fh_i < sizeof(filehandles) / sizeof(*filehandles); fh_i++) {
@@ -126,9 +130,11 @@ void remove_filehandle(FileHandle *file)
         }
     }
     filehandle_mutex->unlock();
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 }
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 #if DEVICE_SERIAL
 extern int stdio_uart_inited;
 extern serial_t stdio_uart;
@@ -391,9 +397,11 @@ static int reserve_filehandle()
 
     return fh_i;
 }
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 int mbed::bind_to_fd(FileHandle *fh)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     int fildes = reserve_filehandle();
     if (fildes < 0) {
         return fildes;
@@ -404,19 +412,27 @@ int mbed::bind_to_fd(FileHandle *fh)
     stdio_out_prev[fildes] = 0;
 
     return fildes;
+#else
+    return -1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
 static int unbind_from_fd(int fd, FileHandle *fh)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     if (filehandles[fd] == fh) {
         filehandles[fd] = NULL;
         return 0;
     } else {
         errno = EBADF;
         return -1;
     }
+#else
+    return -1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
+
 #ifndef __IAR_SYSTEMS_ICC__
 /* IAR provides fdopen itself */
 extern "C" std::FILE *fdopen(int fildes, const char *mode)
@@ -456,6 +472,40 @@ std::FILE *fdopen(FileHandle *fh, const char *mode)
 }
 }
 
+#if MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY
+/** Write the contents of a buffer to a serial interface
+ *
+ *
+ * * if blocking, block until all data is written
+ * * if no data can be written, and nonblocking set, return -EAGAIN
+ * * if some data can be written, and nonblocking set, write partial
+ *
+ *  @param buffer   The buffer to write from
+ *  @param length   The number of bytes to read
+ *  @return         The number of bytes written, negative error on failure
+ */
+static ssize_t mbed_serial_write(const void *buffer, size_t size)
+{
+    ssize_t ret = 0;
+    const unsigned char *buf = static_cast<const unsigned char *>(buffer);
+    static RawSerial console(
+        STDIO_UART_TX,
+        STDIO_UART_RX,
+        MBED_CONF_PLATFORM_STDIO_BAUD_RATE
+    );
+
+    for (size_t i = 0; i < size; i++) {
+        ret = console.putc(buf[i]);
+        if (ret) {
+            break;
+        }
+    }
+
+    return ret;
+}
+#endif // MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY
+
+
 /* @brief   standard c library fopen() retargeting function.
  *
  * This function is invoked by the standard c library retargeting to handle fopen()
@@ -469,6 +519,7 @@ std::FILE *fdopen(FileHandle *fh, const char *mode)
  * */
 extern "C" FILEHANDLE PREFIX(_open)(const char *name, int openflags)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 #if defined(__MICROLIB) && (__ARMCC_VERSION>5030000)
 #if !defined(MBED_CONF_RTOS_PRESENT)
     // valid only for mbed 2
@@ -516,8 +567,13 @@ extern "C" FILEHANDLE PREFIX(_open)(const char *name, int openflags)
     }
 #endif
     return open(name, openflags_to_posix(openflags));
+#else
+    // Everything goes to the same output
+    return 1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 extern "C" int open(const char *name, int oflag, ...)
 {
     int fildes = reserve_filehandle();
@@ -554,12 +610,18 @@ extern "C" int open(const char *name, int oflag, ...)
 
     return fildes;
 }
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 extern "C" int PREFIX(_close)(FILEHANDLE fh)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     return close(fh);
+#else
+    return 0;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 extern "C" int close(int fildes)
 {
     FileHandle *fhc = mbed_file_handle(fildes);
@@ -588,6 +650,7 @@ static bool convert_crlf(int fd)
     return false;
 #endif
 }
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 #if defined(__ICCARM__)
 extern "C" size_t    __write(int        fh, const unsigned char *buffer, size_t length)
@@ -603,6 +666,7 @@ extern "C" int PREFIX(_write)(FILEHANDLE fh, const unsigned char *buffer, unsign
     }
 #endif
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     if (length > SSIZE_MAX) {
         errno = EINVAL;
         return -1;
@@ -669,11 +733,15 @@ extern "C" int PREFIX(_write)(FILEHANDLE fh, const unsigned char *buffer, unsign
 #else
     return written;
 #endif
+
+#else
+    return mbed_serial_write(buffer, length);
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
 extern "C" ssize_t write(int fildes, const void *buf, size_t length)
 {
-
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     FileHandle *fhc = mbed_file_handle(fildes);
     if (fhc == NULL) {
         errno = EBADF;
@@ -687,6 +755,9 @@ extern "C" ssize_t write(int fildes, const void *buf, size_t length)
     } else {
         return ret;
     }
+#else
+    return mbed_serial_write(buf, length);
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
 #if defined (__ARMCC_VERSION) && (__ARMCC_VERSION >= 6010050)
@@ -698,7 +769,11 @@ extern "C" void PREFIX(_exit)(int return_code)
 extern "C" void _ttywrch(int ch)
 {
     char c = ch;
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     write(STDOUT_FILENO, &c, 1);
+#else
+    mbed_serial_write(&c, 1);
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 #endif
 
@@ -710,6 +785,7 @@ extern "C" int PREFIX(_read)(FILEHANDLE fh, unsigned char *buffer, unsigned int
 {
 #endif
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 #if defined(MBED_TRAP_ERRORS_ENABLED) && MBED_TRAP_ERRORS_ENABLED && defined(MBED_CONF_RTOS_PRESENT)
     if (core_util_is_isr_active() || !core_util_are_interrupts_enabled()) {
         MBED_ERROR1(MBED_MAKE_ERROR(MBED_MODULE_PLATFORM, MBED_ERROR_CODE_PROHIBITED_IN_ISR_CONTEXT), "Error - reading from a file in an ISR or critical section\r\n", fh);
@@ -764,8 +840,13 @@ extern "C" int PREFIX(_read)(FILEHANDLE fh, unsigned char *buffer, unsigned int
 #else
     return bytes_read;
 #endif
+#else
+    // Not supported
+    return -1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 extern "C" ssize_t read(int fildes, void *buf, size_t length)
 {
     FileHandle *fhc = mbed_file_handle(fildes);
@@ -782,7 +863,7 @@ extern "C" ssize_t read(int fildes, void *buf, size_t length)
         return ret;
     }
 }
-
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 #ifdef __ARMCC_VERSION
 extern "C" int PREFIX(_istty)(FILEHANDLE fh)
@@ -795,6 +876,7 @@ extern "C" int _isatty(FILEHANDLE fh)
 
 extern "C" int isatty(int fildes)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     FileHandle *fhc = mbed_file_handle(fildes);
     if (fhc == NULL) {
         errno = EBADF;
@@ -808,6 +890,10 @@ extern "C" int isatty(int fildes)
     } else {
         return tty;
     }
+#else
+    // Is not attached to an interactive device
+    return 0;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
 extern "C"
@@ -819,6 +905,7 @@ long __lseek(int fh, long offset, int whence)
 int _lseek(FILEHANDLE fh, int offset, int whence)
 #endif
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 #if defined(__ARMCC_VERSION)
     int whence = SEEK_SET;
 #endif
@@ -832,8 +919,13 @@ int _lseek(FILEHANDLE fh, int offset, int whence)
         return -1;
     }
     return off;
+#else
+    // Not supported
+    return -1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 extern "C" off_t lseek(int fildes, off_t offset, int whence)
 {
     FileHandle *fhc = mbed_file_handle(fildes);
@@ -873,9 +965,11 @@ extern "C" int PREFIX(_ensure)(FILEHANDLE fh)
     return fsync(fh);
 }
 #endif
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 extern "C" int fsync(int fildes)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     FileHandle *fhc = mbed_file_handle(fildes);
     if (fhc == NULL) {
         errno = EBADF;
@@ -889,11 +983,15 @@ extern "C" int fsync(int fildes)
     } else {
         return 0;
     }
+#else
+    return -1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
 #ifdef __ARMCC_VERSION
 extern "C" long PREFIX(_flen)(FILEHANDLE fh)
 {
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
     FileHandle *fhc = mbed_file_handle(fh);
     if (fhc == NULL) {
         errno = EBADF;
@@ -910,6 +1008,10 @@ extern "C" long PREFIX(_flen)(FILEHANDLE fh)
         return -1;
     }
     return size;
+#else
+    // Not supported
+    return -1;
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 }
 
 // Do not compile this code for TFM secure target
@@ -983,7 +1085,7 @@ extern "C" __value_in_regs struct __initial_stackheap __user_setup_stackheap(uin
 
 #endif
 
-
+#if !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 #if !defined(__ARMCC_VERSION) && !defined(__ICCARM__)
 extern "C" int _fstat(int fh, struct stat *st)
 {
@@ -1060,6 +1162,7 @@ extern "C" int poll(struct pollfd fds[], nfds_t nfds, int timeout)
     }
     return ret;
 }
+#endif // !(MBED_CONF_PLATFORM_STDIO_CONSOLE_ONLY)
 
 namespace std {
 extern "C" int remove(const char *path)