Bug #52
Repeated gdp_gcl_open calls on non-existing GCLs do not give proper error code (was: GDP_GCL() function in Python does not raise an error when opening a non-existing GCL)
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Description
When opening a non-existing GCL, the gdp.GDP_GCL function in the Python API only raises an error during the first attempt. However, if you try to open it again, it will not raise an error.
Sample code:
gdp.gdp_init()
gcl_name = gdp.GDP_NAME("this.GCL.does.not.exist")
gcl_handle = gdp.GDP_GCL(gcl_name, gdp.GDP_MODE_RO) #this will raise an error
gcl_handle = gdp.GDP_GCL(gcl_name, gdp.GDP_MODE_RO) #this will NOT raise an error
This was still working with my Feb 2016 copy of the codes.
History
#1 Updated by Rico Maestro over 6 years ago
- Project changed from Click GDP Routers to GDP
- Category set to Python API
#2 Updated by Nitesh Mor over 6 years ago
- File multi-open.c
added - Category changed from Python API to libgdp
- Assignee changed from Nitesh Mor to Eric Allman
Good point. There was a minor change in GDP_GCL(...) to better match it with the underlying C-API behavior. More specifically, the underlying C-API re-uses the data-structures if you open the same GCL multiple times (potentially from different threads, but not necessarily). Before commit commit:68ee5384, the Python API neglected such re-use, which meant that a single underlying C data-structure gdp_gcl_t could be mapped to multiple python GDP_GCL objects, causing numerous issues.
It turns out that this is a bug in the underlying C library, which failed to show up so far. Here's what happens in C:
// Opening GCL for the first time
estat = gdp_gcl_open(gclname, GDP_MODE_RO, NULL, &gcl);
if (!EP_STAT_ISOK(estat))
printf("Expected behavior, EP_STAT is erroneous\n");
// Opening the same GCL again
estat = gdp_gcl_open(gclname, GDP_MODE_RO, NULL, &gcl);
if (!EP_STAT_ISOK(estat))
{
printf("Expected behavior, EP_STAT is erroneous\n");
}
else
{
char buf[100];
ep_stat_tostr(estat, buf, 100);
printf("Unexpected behavior. EP_STAT: %s\n", buf);
}
The output is:
Expected behavior, EP_STAT is erroneous Unexpected behavior. EP_STAT: OK
See attached for a full sample code. Assigning this to Eric.
#3 Updated by Eric Allman over 6 years ago
- File multi-open.c added
- Subject changed from GDP_GCL() function in Python does not raise an error when opening a non-existing GCL to Repeated gdp_gcl_open calls on non-existing GCLs do not give proper error code (was: GDP_GCL() function in Python does not raise an error when opening a non-existing GCL)
- Status changed from New to Feedback
Problem was that the unopened GCL was being kept in the cache; the subsequent calls to gdp_gcl_open found the cached version and assumed it was correct. There were two possible solutions: mark the cached version as failed, or remove the cache entry entirely. I opted for the latter, since someone could come along later and fix the problem. Fixed in commit:079043b8.
There's also an improved version of the test program attached that lets you set debugging without recompiling.
#4 Updated by Nitesh Mor over 6 years ago
- Status changed from Feedback to Closed
Seems to work. Closing the issue.