Re: shuf.c build failures -- trivial code issue

[Paul Eggert]

Thanks for catching that.  I installed the following patch:

2006-08-09  Paul Eggert  <address@hidden>

        * src/shuf.c (next_line): New function.
        (read_input): Use it, to avoid relying on GCC-specific behavior
        with void * arithmetic.  Problem reported by Bob Proulx.
        * Makefile.maint (my-distcheck): Compile with -Wpointer-arith
        to detect this sort of problem automatically in the future.

Index: src/shuf.c
===================================================================
RCS file: /fetish/cu/src/shuf.c,v
retrieving revision 1.1
diff -p -u -r1.1 shuf.c
--- src/shuf.c  8 Aug 2006 22:22:48 -0000       1.1
+++ src/shuf.c  9 Aug 2006 18:07:04 -0000
@@ -129,6 +129,16 @@ input_from_argv (char **operand, int n_o
   operand[n_operands] = p;
 }
 
+/* Return the start of the next line after LINE.  The current line
+   ends in EOLBYTE, and is guaranteed to end before LINE + N.  */
+
+static char *
+next_line (char *line, char eolbyte, size_t n)
+{
+  char *p = memchr (line, eolbyte, n);
+  return p + 1;
+}
+
 /* Read data from file IN.  Input lines are delimited by EOLBYTE;
    silently append a trailing EOLBYTE if the file ends in some other
    byte.  Store a pointer to the resulting array of lines into *PLINE.
@@ -193,14 +203,14 @@ read_input (FILE *in, char eolbyte, char
   lim = buf + used;
 
   n_lines = 0;
-  for (p = buf; p < lim; p = memchr (p, eolbyte, lim - p) + 1)
+  for (p = buf; p < lim; p = next_line (p, eolbyte, lim - p))
     n_lines++;
 
   *pline = line = xnmalloc (n_lines + 1, sizeof *line);
 
   line[0] = p = buf;
   for (i = 1; i <= n_lines; i++)
-    line[i] = p = memchr (p, eolbyte, lim - p) + 1;
+    line[i] = p = next_line (p, eolbyte, lim - p);
 
   errno = fread_errno;
   return n_lines;
Index: Makefile.maint
===================================================================
RCS file: /fetish/cu/Makefile.maint,v
retrieving revision 1.238
diff -p -u -r1.238 Makefile.maint
--- Makefile.maint      19 Jul 2006 08:43:27 -0000      1.238
+++ Makefile.maint      9 Aug 2006 18:07:04 -0000
@@ -450,7 +450,8 @@ null_AM_MAKEFLAGS = \
 # Detect format-string/arg-list mismatches that would normally be obscured
 # by the use of _().  The --disable-nls effectively defines away that macro,
 # and building with CFLAGS='-Wformat -Werror' causes any format warning to be
-# treated as a failure.  Also, check for shadowing problems with -Wshadow.
+# treated as a failure.  Also, check for shadowing problems with -Wshadow,
+# and for pointer arithmetic problems with -Wpointer-arith.
 # These CFLAGS are pretty strict.  If you build this target, you probably
 # have to have a recent version of gcc and glibc headers.
 TMPDIR ?= /tmp
@@ -461,7 +462,7 @@ my-distcheck: $(local-check) $(release_a
        GZIP=$(GZIP_ENV) $(AMTAR) -C $(t) -zxf $(distdir).tar.gz
        cd $(t)/$(distdir)                              \
          && ./configure --disable-nls                  \
-         && $(MAKE) CFLAGS='-Werror -Wall -Wformat -Wshadow' \
+         && $(MAKE) CFLAGS='-Werror -Wall -Wformat -Wshadow -Wpointer-arith' \
              AM_MAKEFLAGS='$(null_AM_MAKEFLAGS)'       \
          && $(MAKE) dvi                                \
          && $(MAKE) check                              \