read.table problem on Linux/Alpha (seg faults caused by isspace(R_EOF)) (PR#303)

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Subject: read.table problem on Linux/Alpha (seg faults caused by isspace(R_EOF)) (PR#303)
ntakebay@bio.indiana.edu
Date: Sun 31 Oct 1999 - 09:29:06 EST


Message-Id: <199910302329.BAA17382@pubhealth.ku.dk>

Full_Name: Naoki Takebayashi
Version: 0.65.1
OS: Linux/Alpha
Submission from: (NULL) (129.79.224.171)

When I was reading a file with read.table("junk.data"), it seg-faulted.
I found out that it seg-faulted when the last line of data file didn't
have the newline char. For example, file like this:

23 3
31 2
24 1<EOF>

Here is a fix.

--- R-0.65.1/src/main/scan.c.orig Wed Sep 29 11:11:45 1999
+++ R-0.65.1/src/main/scan.c Fri Oct 29 17:34:22 1999
@@ -124,7 +124,7 @@
                if (bufp >= &buffer[MAXELTSIZE - 2])
                    continue;
                *bufp++ = c;
- } while (!isspace(c = scanchar()) && c != R_EOF);
+ } while ((c = scanchar()) != R_EOF && !isspace(c));
            while (c==' ' || c=='\t')
                c=scanchar();
            if (c=='\n' || c=='\r' || c==R_EOF)
@@ -647,7 +647,7 @@
                }
            }
            else {
- while (!isspace(c=scanchar()) && c != R_EOF)
+ while ( (c=scanchar()) != R_EOF && !isspace(c))
                    ;
                if (c==R_EOF) c='\n';
                unscanchar(c);

When the scanchar() returns R_EOF (=65535 #defined in src/include/Defn.h),
isspace(R_EOF) seq-faults. By switching the order of two conditions, I could
get around with it. I just made a test to see the behavior of isspace() by
giving
isspace(65535). It seg-faults in both Linux/alpha and i386 (is it supposed
to??).
However, R on i386 doesn't seg-faults when the last line does not have newline.

Naoki

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