tests: fix reading the output of subprocesses

We're currently using vasprintf() internally when reading the output
streams of terminated subprocesses. This routine interprets the buffer
as a printf() format string, so substrings like '%x' get converted
unintentionally.

Instead allocate a big enough buffer and just read the output without
any modifications.

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>

diff --git a/tests/gpiod-test.c b/tests/gpiod-test.c
index 3571a6ddee0116aa9921632f3f834600465ce34f..517f0171e8080d71eb092e98e5ec739ab345bd39 100644 (file)
--- a/tests/gpiod-test.c
+++ b/tests/gpiod-test.c
@@ -15,6 +15,7 @@
 #include <stdarg.h>
 #include <errno.h>
 #include <unistd.h>
+#include <fcntl.h>
 #include <poll.h>
 #include <signal.h>
 #include <libgen.h>
@@ -551,25 +552,37 @@ void test_tool_run(char *tool, ...)
 
 static void gpiotool_readall(int fd, char **out)
 {
-       char buf[1024], *tmp = NULL;
        ssize_t rd;
+       char *buf;
+       int psiz;
 
-       for (;;) {
-               memset(buf, 0, sizeof(buf));
-               rd = read(fd, buf, sizeof(buf));
-               if (rd < 0)
-                       die_perr("error reading output from subprocess");
-               else if (rd == 0) {
-                       *out = tmp;
-                       return;
-               }
+       /*
+        * Since linux v2.6.11 the default pipe capacity is 16 system pages.
+        * We make an assumption here, that gpio-tools won't output more than
+        * that, so we can read everything after the program terminated. If
+        * they did output more than the pipe capacity however, the write()
+        * would block and the process would be killed by the testing
+        * framework.
+        */
+       psiz = fcntl(fd, F_GETPIPE_SZ);
+       if (psiz < 0)
+               die_perr("error retrieving the pipe capacity");
 
-               /*
-                * FIXME This may lead to errors if the program prints
-                * a string containing printf() format specifiers.
-                */
-               tmp = xappend(tmp, buf);
-       }
+       buf = malloc(psiz);
+       if (!buf)
+               die("out of memory");
+
+       memset(buf, 0, psiz);
+       rd = read(fd, buf, psiz);
+       if (rd < 0)
+               die_perr("error reading output from subprocess");
+       else if (rd == 0)
+               *out = NULL;
+       else
+               *out = buf;
+
+       if (!*out)
+               free(buf);
 }
 
 void test_tool_wait(void)