Lisandro,

As a matter of personal taste, I prefer that empty strings be used as initializers for C strings.  One of the things I dislike extremely about C (and, one of the reasons I think it is so easy in C to write bad code) is its mixing of integers and pointers and integers and chars.  Even though { 0 } is identical to { "" } when initializing C strings, I find the latter more informative.  I know the C standard specifies that strings are terminated by the null character, which is elsewhere specified to be a byte with all bits equal to zero.  However, "" is the literal empty string, whereas 0 (or '\0') is the underlying implementation of the empty string.  This is also why I prefer to use the C99 NULL macro constant to initialize pointers with the nil pointer as opposed to 0 (which gets implicitly cast to a nil pointer of the correct size), the implementation of the nil pointer.  As I said, though, this is all just a matter of taste -- there is no difference in the correctness of the code.

Larry Baker
US Geological Survey
650-329-5608
baker@usgs.gov

On 23 Apr 2014, at 3:20 AM, Lisandro Dalcin wrote:

On 23 April 2014 00:55, Rob Latham <robl@mcs.anl.gov> wrote:

On 04/22/2014 04:04 AM, Lisandro Dalcin wrote:

The following simple tests segfaults. A quick fix would be to return

an empty string in MPIR_Err_get_dynerr_string() (file dynerrutil.c),

I don't muck around in this code very often, so after thinking about it for

a bit, and coming up with another way to do it, I opened a ticket so i could

get a second (third, I guess) opinion:

https://trac.mpich.org/projects/mpich/ticket/2067

IMHO your patch complicates things too much, I'm still in support of
this slightly refined version that removes the usage of empty string
constants (Rob, could you upload this patch to the ticket?):

$ git diff
diff --git a/src/mpi/errhan/dynerrutil.c b/src/mpi/errhan/dynerrutil.c
index 943e8c3..2e3bb27 100644
--- a/src/mpi/errhan/dynerrutil.c
+++ b/src/mpi/errhan/dynerrutil.c
@@ -48,6 +48,7 @@ static const char
*(user_class_msgs[ERROR_MAX_NCLASS]) = { 0 };
static const char *(user_code_msgs[ERROR_MAX_NCODE]) = { 0 };
static int  first_free_class = 0;
static int  first_free_code  = 1;  /* code 0 is reserved */
+static const char empty_error_string[1] = { 0 };

/* Forward reference */
const char *MPIR_Err_get_dynerr_string( int code );
@@ -297,11 +298,13 @@ const char *MPIR_Err_get_dynerr_string( int code )
    if (errcode) {
 if (errcode < first_free_code) {
    errstr = user_code_msgs[errcode];
+    if (!errstr) errstr = empty_error_string;
 }
    }
    else {
 if (errclass < first_free_class) {
    errstr = user_class_msgs[errclass];
+    if (!errstr) errstr = empty_error_string;
 }
    }



--
Lisandro Dalcin
---------------
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<error-string.diff>