scpi_vxi: fix memory leak for SCPI response data in VXI support code

Routine scpi_vxi_read_data() invokes device_read_1(), which provides a
static buffer where dynamically allocated memory for SCPI response data
is kept. Release this memory after getting a copy of the response data,
before the next device_read_1() call loses the reference.

Valgrind stats without the fix:

  ==238825== LEAK SUMMARY:
  ==238825== definitely lost: 45,547,737 bytes in 18,331 blocks
  ==238825== indirectly lost: 0 bytes in 0 blocks
  ==238825== possibly lost: 48,154 bytes in 14 blocks
  ==238825== still reachable: 42,859 bytes in 288 blocks
  ==238825== suppressed: 0 bytes in 0 blocks

Valgrind stats with the fix:

  ==239413== LEAK SUMMARY:
  ==239413== definitely lost: 40 bytes in 2 blocks
  ==239413== indirectly lost: 0 bytes in 0 blocks
  ==239413== possibly lost: 0 bytes in 0 blocks
  ==239413== still reachable: 38,613 bytes in 287 blocks
  ==239413== suppressed: 0 bytes in 0 blocks

Remaining leaks in scpi_vxi_open() are of lesser severity because they
don't accumulate during execution.

[ gsi: rebase to recent master, reword commit message ]

diff --git a/src/scpi/scpi_vxi.c b/src/scpi/scpi_vxi.c
index 2b8e50dee5688ce3a7383e29949ee959086d5dc2..9b38efdab1c83581146b3fe5a0344019bce49d44 100644 (file)
--- a/src/scpi/scpi_vxi.c
+++ b/src/scpi/scpi_vxi.c
@@ -195,10 +195,16 @@ static int scpi_vxi_read_data(void *priv, char *buf, int maxlen)
        if (!read_resp || read_resp->error) {
                sr_err("Device read failed for %s with error %ld",
                       vxi->address, read_resp ? read_resp->error : 0);
+               if (read_resp) {
+                       g_free(read_resp->data.data_val);
+                       read_resp->data.data_val = NULL;
+               }
                return SR_ERR;
        }
 
        memcpy(buf, read_resp->data.data_val, read_resp->data.data_len);
+       g_free(read_resp->data.data_val);
+       read_resp->data.data_val = NULL;
        vxi->read_complete = read_resp->reason & (RRR_TERM | RRR_END);
        return read_resp->data.data_len;  /* actual number of bytes received */
 }