Fortran: simplify library code for integer-to-decimal conversion

libgfortran/ChangeLog:

	PR libfortran/81986
	PR libfortran/99191

	* libgfortran.h: Remove gfc_xtoa(), adjust gfc_itoa() and
	GFC_ITOA_BUF_SIZE.
	* io/write.c (write_decimal): conversion parameter is always
	gfc_itoa(), so remove it. Protect from overflow.
	(xtoa): Move gfc_xtoa and update its name.
	(xtoa_big): Renamed from ztoa_big for consistency.
	(write_z): Adjust to new function names.
	(write_i, write_integer): Remove last arg of write_decimal.
	* runtime/backtrace.c (error_callback): Comment on the use of
	gfc_itoa().
	* runtime/error.c (gfc_xtoa): Move to io/write.c.
	* runtime/string.c (gfc_itoa): Take an unsigned argument,
	remove the handling of negative values.

3 files changed, 16 insertions, 55 deletions

diff --git a/libgfortran/runtime/backtrace.c b/libgfortran/runtime/backtrace.c
index 5ac0831..403c7c3 100644
--- a/libgfortran/runtime/backtrace.c
+++ b/libgfortran/runtime/backtrace.c
@@ -97,6 +97,7 @@ error_callback (void *data, const char *msg, int errnum)
 	  iov[1].iov_len = strlen (msg);
 	  iov[2].iov_base = (char*) ", errno: ";
 	  iov[2].iov_len = strlen (iov[2].iov_base);
+	  /* Async-signal-safe function, errnum must be positive.  */
 	  const char *p = gfc_itoa (errnum, errbuf, sizeof (errbuf));
 	  iov[3].iov_base = (char*) p;
 	  iov[3].iov_len = strlen (p);
diff --git a/libgfortran/runtime/error.c b/libgfortran/runtime/error.c
index b9c7574..ba6ff86 100644
--- a/libgfortran/runtime/error.c
+++ b/libgfortran/runtime/error.c
@@ -219,37 +219,6 @@ exit_error (int status)
 }
 
 
-
-/* gfc_xtoa()-- Integer to hexadecimal conversion.  */
-
-const char *
-gfc_xtoa (GFC_UINTEGER_LARGEST n, char *buffer, size_t len)
-{
-  int digit;
-  char *p;
-
-  assert (len >= GFC_XTOA_BUF_SIZE);
-
-  if (n == 0)
-    return "0";
-
-  p = buffer + GFC_XTOA_BUF_SIZE - 1;
-  *p = '\0';
-
-  while (n != 0)
-    {
-      digit = n & 0xF;
-      if (digit > 9)
-	digit += 'A' - '0' - 10;
-
-      *--p = '0' + digit;
-      n >>= 4;
-    }
-
-  return p;
-}
-
-
 /* Hopefully thread-safe wrapper for a strerror() style function.  */
 
 char *
diff --git a/libgfortran/runtime/string.c b/libgfortran/runtime/string.c
index 536a9cd..835027a 100644
--- a/libgfortran/runtime/string.c
+++ b/libgfortran/runtime/string.c
@@ -169,21 +169,22 @@ find_option (st_parameter_common *cmp, const char *s1, gfc_charlen_type s1_len,
 }
 
 
-/* gfc_itoa()-- Integer to decimal conversion.
-   The itoa function is a widespread non-standard extension to
-   standard C, often declared in <stdlib.h>.  Even though the itoa
-   defined here is a static function we take care not to conflict with
-   any prior non-static declaration.  Hence the 'gfc_' prefix, which
-   is normally reserved for functions with external linkage.  Notably,
-   in contrast to the *printf() family of functions, this ought to be
-   async-signal-safe.  */
+/* Integer to decimal conversion.
+
+   This function is much more restricted than the widespread (but
+   non-standard) itoa() function.  This version has the following
+   characteristics:
+
+     - it takes only non-negative arguments
+     - it is async-signal-safe (we use it runtime/backtrace.c)
+     - it works in base 10 (see xtoa, otoa, btoa functions
+       in io/write.c for other radices)
+ */
 
 const char *
-gfc_itoa (GFC_INTEGER_LARGEST n, char *buffer, size_t len)
+gfc_itoa (GFC_UINTEGER_LARGEST n, char *buffer, size_t len)
 {
-  int negative;
   char *p;
-  GFC_UINTEGER_LARGEST t;
 
   if (len < GFC_ITOA_BUF_SIZE)
     sys_abort ();
@@ -191,24 +192,14 @@ gfc_itoa (GFC_INTEGER_LARGEST n, char *buffer, size_t len)
   if (n == 0)
     return "0";
 
-  negative = 0;
-  t = n;
-  if (n < 0)
-    {
-      negative = 1;
-      t = -(GFC_UINTEGER_LARGEST) n;  /* Must use unsigned to protect from overflow. */
-    }
-
   p = buffer + GFC_ITOA_BUF_SIZE - 1;
   *p = '\0';
 
-  while (t != 0)
+  while (n != 0)
     {
-      *--p = '0' + (t % 10);
-      t /= 10;
+      *--p = '0' + (n % 10);
+      n /= 10;
     }
 
-  if (negative)
-    *--p = '-';
   return p;
 }