Avoid undefined behavior in signed left shift.

This ports to GCC 4.9.0 with -fsanitize=undefined.
* alloc.c (bool_vector_fill, SETMARKBIT, UNSETMARKBIT):
* data.c (Fash):
* regex.c (extract_number):
* lisp.h (make_number, XINT):
Do not shift a 1 bit left into a sign bit.
* alloc.c (struct cons_block, struct float_block): Use unsigned,
not int, for gcmarkbits.  All uses changed.

diff --git a/src/ChangeLog b/src/ChangeLog
index 9d4fd2d..90223d6 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,15 @@
+2014-04-28  Paul Eggert  <eggert@cs.ucla.edu>
+
+       Avoid undefined behavior in signed left shift.
+       This ports to GCC 4.9.0 with -fsanitize=undefined.
+       * alloc.c (bool_vector_fill, SETMARKBIT, UNSETMARKBIT):
+       * data.c (Fash):
+       * regex.c (extract_number):
+       * lisp.h (make_number, XINT):
+       Do not shift a 1 bit left into a sign bit.
+       * alloc.c (struct cons_block, struct float_block): Use unsigned,
+       not int, for gcmarkbits.  All uses changed.
+
 2014-04-25  Eli Zaretskii  <eliz@gnu.org>
 
        * search.c (Fnewline_cache_check): Don't try to count newlines

diff --git a/src/alloc.c b/src/alloc.c
index 6bee0c9..32d3333 100644 (file)
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -2131,7 +2131,7 @@ bool_vector_fill (Lisp_Object a, Lisp_Object init)
       unsigned char *data = bool_vector_uchar_data (a);
       int pattern = NILP (init) ? 0 : (1 << BOOL_VECTOR_BITS_PER_CHAR) - 1;
       ptrdiff_t nbytes = bool_vector_bytes (nbits);
-      int last_mask = ~ (~0 << ((nbits - 1) % BOOL_VECTOR_BITS_PER_CHAR + 1));
+      int last_mask = ~ (~0u << ((nbits - 1) % BOOL_VECTOR_BITS_PER_CHAR + 1));
       memset (data, pattern, nbytes - 1);
       data[nbytes - 1] = pattern & last_mask;
     }
@@ -2336,17 +2336,17 @@ make_formatted_string (char *buf, const char *format, ...)
    / (sizeof (struct Lisp_Float) * CHAR_BIT + 1))
 
 #define GETMARKBIT(block,n)                            \
-  (((block)->gcmarkbits[(n) / (sizeof (int) * CHAR_BIT)]       \
-    >> ((n) % (sizeof (int) * CHAR_BIT)))              \
+  (((block)->gcmarkbits[(n) / (sizeof (unsigned) * CHAR_BIT)]  \
+    >> ((n) % (sizeof (unsigned) * CHAR_BIT)))         \
    & 1)
 
 #define SETMARKBIT(block,n)                            \
-  (block)->gcmarkbits[(n) / (sizeof (int) * CHAR_BIT)] \
-  |= 1 << ((n) % (sizeof (int) * CHAR_BIT))
+  ((block)->gcmarkbits[(n) / (sizeof (unsigned) * CHAR_BIT)]   \
+   |= 1u << ((n) % (sizeof (unsigned) * CHAR_BIT)))
 
 #define UNSETMARKBIT(block,n)                          \
-  (block)->gcmarkbits[(n) / (sizeof (int) * CHAR_BIT)] \
-  &= ~(1 << ((n) % (sizeof (int) * CHAR_BIT)))
+  ((block)->gcmarkbits[(n) / (sizeof (unsigned) * CHAR_BIT)]   \
+   &= ~(1u << ((n) % (sizeof (unsigned) * CHAR_BIT))))
 
 #define FLOAT_BLOCK(fptr) \
   ((struct float_block *) (((uintptr_t) (fptr)) & ~(BLOCK_ALIGN - 1)))
@@ -2358,7 +2358,7 @@ struct float_block
 {
   /* Place `floats' at the beginning, to ease up FLOAT_INDEX's job.  */
   struct Lisp_Float floats[FLOAT_BLOCK_SIZE];
-  int gcmarkbits[1 + FLOAT_BLOCK_SIZE / (sizeof (int) * CHAR_BIT)];
+  unsigned gcmarkbits[1 + FLOAT_BLOCK_SIZE / (sizeof (unsigned) * CHAR_BIT)];
   struct float_block *next;
 };
 
@@ -2452,7 +2452,7 @@ struct cons_block
 {
   /* Place `conses' at the beginning, to ease up CONS_INDEX's job.  */
   struct Lisp_Cons conses[CONS_BLOCK_SIZE];
-  int gcmarkbits[1 + CONS_BLOCK_SIZE / (sizeof (int) * CHAR_BIT)];
+  unsigned gcmarkbits[1 + CONS_BLOCK_SIZE / (sizeof (unsigned) * CHAR_BIT)];
   struct cons_block *next;
 };
 

diff --git a/src/data.c b/src/data.c
index 965ddd2..bf863aa 100644 (file)
--- a/src/data.c
+++ b/src/data.c
@@ -2895,7 +2895,7 @@ In this case, the sign bit is duplicated.  */)
   if (XINT (count) >= BITS_PER_EMACS_INT)
     XSETINT (val, 0);
   else if (XINT (count) > 0)
-    XSETINT (val, XINT (value) << XFASTINT (count));
+    XSETINT (val, XUINT (value) << XFASTINT (count));
   else if (XINT (count) <= -BITS_PER_EMACS_INT)
     XSETINT (val, XINT (value) < 0 ? -1 : 0);
   else

diff --git a/src/lisp.h b/src/lisp.h
index 4c310f6..5e0f141 100644 (file)
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -354,7 +354,8 @@ error !;
 # define lisp_h_check_cons_list() ((void) 0)
 #endif
 #if USE_LSB_TAG
-# define lisp_h_make_number(n) XIL ((EMACS_INT) (n) << INTTYPEBITS)
+# define lisp_h_make_number(n) \
+    XIL ((EMACS_INT) ((EMACS_UINT) (n) << INTTYPEBITS))
 # define lisp_h_XFASTINT(a) XINT (a)
 # define lisp_h_XINT(a) (XLI (a) >> INTTYPEBITS)
 # define lisp_h_XTYPE(a) ((enum Lisp_Type) (XLI (a) & ~VALMASK))
@@ -665,7 +666,14 @@ LISP_MACRO_DEFUN (XUNTAG, void *, (Lisp_Object a, int type), (a, type))
 INLINE Lisp_Object
 make_number (EMACS_INT n)
 {
-  return XIL (USE_LSB_TAG ? n << INTTYPEBITS : n & INTMASK);
+  if (USE_LSB_TAG)
+    {
+      EMACS_UINT u = n;
+      n = u << INTTYPEBITS;
+    }
+  else
+    n &= INTMASK;
+  return XIL (n);
 }
 
 /* Extract A's value as a signed integer.  */
@@ -673,7 +681,12 @@ INLINE EMACS_INT
 XINT (Lisp_Object a)
 {
   EMACS_INT i = XLI (a);
-  return (USE_LSB_TAG ? i : i << INTTYPEBITS) >> INTTYPEBITS;
+  if (! USE_LSB_TAG)
+    {
+      EMACS_UINT u = i;
+      i = u << INTTYPEBITS;
+    }
+  return i >> INTTYPEBITS;
 }
 
 /* Like XINT (A), but may be faster.  A must be nonnegative.

diff --git a/src/regex.c b/src/regex.c
index 2449240..622db70 100644 (file)
--- a/src/regex.c
+++ b/src/regex.c
@@ -713,7 +713,8 @@ typedef enum
 static int
 extract_number (re_char *source)
 {
-  return (SIGN_EXTEND_CHAR (source[1]) << 8) + source[0];
+  unsigned leading_byte = SIGN_EXTEND_CHAR (source[1]);
+  return (leading_byte << 8) + source[0];
 }
 
 /* Same as EXTRACT_NUMBER, except increment SOURCE to after the number.