Patch brings strtol() and related functions more conformant with POSIX. Corner cases like strtol(-2147483648, NULL, 10) now pass clang -fsanitize=integer without warnings.

libc/stdlib/lib_strtol.c

@@ -41,6 +41,7 @@
 
 #include <stdbool.h>
 #include <stdlib.h>
+#include <errno.h>
 
 #include "libc.h"
 
@@ -60,7 +61,13 @@
  *   nptr to a long integer value according to the given base, which must be
  *   between 2 and 36 inclusive, or be the special value 0.
  *
- * Warning: does not check for integer overflow!
+ * Returns:
+ *   - The converted value, if the base and number are valid
+ *   - 0 if an error occurs, and set errno to:
+ *     * EINVAL if base < 2 or base > 36
+ *   - LONG_MIN or LONG_MAX, of correct sign, if an overflow occurs,
+ *     and set errno to:
+ *     * ERANGE if the number cannot be represented using long
  *
  ****************************************************************************/
 
@@ -91,11 +98,25 @@ long strtol(FAR const char *nptr, FAR char **endptr, int base)
 
       accum = strtoul(nptr, endptr, base);
 
-      /* Correct the sign of the result */
+      /* Correct the sign of the result and check for overflow */
 
       if (negate)
         {
-          return -(long)accum;
+          const unsigned long limit = ((unsigned long)-(LONG_MIN + 1)) + 1;
+
+          if (accum > limit)
+            {
+              set_errno(ERANGE);
+              return LONG_MIN;
+            }
+
+          return (accum == limit) ? LONG_MIN : -(long)accum;
+        }
+
+      if (accum > LONG_MAX)
+        {
+          set_errno(ERANGE);
+          return LONG_MAX;
         }
     }
 

libc/stdlib/lib_strtoll.c

@@ -41,6 +41,7 @@
 
 #include <stdbool.h>
 #include <stdlib.h>
+#include <errno.h>
 
 #include "libc.h"
 
@@ -58,11 +59,17 @@
  * Name: strtoll
  *
  * Description:
- *   The  strtol() function  converts  the initial part of the string in
+ *   The strtoll() function  converts  the initial part of the string in
  *   nptr to a long long integer value according to the given base, which
  *   must be between 2 and 36 inclusive, or be the special value 0.
  *
- * Warning: does not check for integer overflow!
+ * Returns:
+ *   - The converted value, if the base and number are valid
+ *   - 0 if an error occurs, and set errno to:
+ *     * EINVAL if base < 2 or base > 36
+ *   - LLONG_MIN or LLONG_MAX, of correct sign, if an overflow occurs,
+ *     and set errno to:
+ *     * ERANGE if the number cannot be represented using long long
  *
  ****************************************************************************/
 
@@ -93,11 +100,25 @@ long long strtoll(FAR const char *nptr, FAR char **endptr, int base)
 
       accum = strtoull(nptr, endptr, base);
 
-      /* Correct the sign of the result */
+      /* Correct the sign of the result and check for overflow */
 
       if (negate)
         {
-          return -(long long)accum;
+          const unsigned long long limit = ((unsigned long long)-(LLONG_MIN + 1)) + 1;
+
+          if (accum > limit)
+            {
+              set_errno(ERANGE);
+              return LLONG_MIN;
+            }
+
+          return (accum == limit) ? LLONG_MIN : -(long long)accum;
+        }
+
+      if (accum > LLONG_MAX)
+        {
+          set_errno(ERANGE);
+          return LLONG_MAX;
         }
     }
 

libc/stdlib/lib_strtoul.c

@@ -52,14 +52,15 @@
  * Name: strtoul
  *
  * Description:
- *   The  strtol() function  converts  the initial part of the string in
+ *   The strtoul() function  converts  the initial part of the string in
  *   nptr to a long unsigned integer value according to the given base, which
  *   must be between 2 and 36 inclusive, or be the special value 0.
  *
  * Returns:
  *   - The converted value, if the base and number are valid
- *   - 0 if an error occurs, and seterrno to:
+ *   - 0 if an error occurs, and set errno to:
  *     * EINVAL if base < 2 or base > 36
+ *   - ULONG_MAX if an overflow occurs, and set errno to:
  *     * ERANGE if the number cannot be represented using unsigned long
  *
  ****************************************************************************/
@@ -99,7 +100,7 @@ unsigned long strtoul(FAR const char *nptr, FAR char **endptr, int base)
           if (accum < prev)
             {
               set_errno(ERANGE);
-              accum = 0;
+              accum = ULONG_MAX;
               break;
             }
         }

libc/stdlib/lib_strtoull.c

@@ -55,14 +55,15 @@
  * Name: strtoull
  *
  * Description:
- *   The  strtol() function  converts  the initial part of the string in
+ *   The strtoull() function  converts  the initial part of the string in
  *   nptr to a long unsigned integer value according to the given base, which
  *   must be between 2 and 36 inclusive, or be the special value 0.
  *
  * Returns:
  *   - The converted value, if the base and number are valid
- *   - 0 if an error occurs, and seterrno to:
+ *   - 0 if an error occurs, and set errno to:
  *     * EINVAL if base < 2 or base > 36
+ *   - ULLONG_MAX if an overflow occurs, and set errno to:
  *     * ERANGE if the number cannot be represented using unsigned long long
  *
  ****************************************************************************/
@@ -102,7 +103,7 @@ unsigned long long strtoull(FAR const char *nptr, FAR char **endptr, int base)
           if (accum < prev)
             {
               set_errno(ERANGE);
-              accum = 0;
+              accum = ULLONG_MAX;
               break;
             }
         }