[PATCH 1/4] Properly test for return-values from read() and write()

[Henrik Austad <haustad@cisco.com>]

It is conceivable that read() and write() will fail, and when they do,
it is useful to catch these errors. This also has the benefit of
removing gcc-warnings like :

warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
      write(tracing_enabled, "0", 1);
            ^
warning: ignoring return value of ‘ftruncate’, declared with attribute warn_unused_result [-Wunused-result]
   ftruncate(shmem, totalsize);
            ^
warning: ignoring return value of ‘read’, declared with attribute warn_unused_result [-Wunused-result]
    read(path, timestamp, sizeof(timestamp));
        ^
Signed-off-by: Henrik Austad <haustad@cisco.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
---
 src/backfire/sendme.c                 | 8 ++++++--
 src/cyclictest/cyclictest.c           | 9 ++++++---
 src/pmqtest/pmqtest.c                 | 3 ++-
 src/ptsematest/ptsematest.c           | 3 ++-
 src/rt-migrate-test/rt-migrate-test.c | 5 +++--
 src/sigwaittest/sigwaittest.c         | 8 ++++++--
 src/svsematest/svsematest.c           | 9 +++++++--
 7 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/backfire/sendme.c b/src/backfire/sendme.c
index c1854d9..34504b7 100644
--- a/src/backfire/sendme.c
+++ b/src/backfire/sendme.c
@@ -256,9 +256,13 @@ int main(int argc, char *argv[])
 			ts.tv_nsec = (interval % USEC_PER_SEC) * 1000;
 
 			gettimeofday(&before, NULL);
-			write(path, sigtest, strlen(sigtest));
+			if (write(path, sigtest, strlen(sigtest)) < 0)
+				fprintf(stderr, "Could not write sigtest to backfire-path\n");
+
 			while (after.tv_sec == 0);
-			read(path, timestamp, sizeof(timestamp));
+			if (read(path, timestamp, sizeof(timestamp)) <= 0)
+				fprintf(stderr, "Trouble reading file backfire-path\n");
+
 			if (sscanf(timestamp, "%lu,%lu\n", &sendtime.tv_sec,
 			    &sendtime.tv_usec) != 2)
 				break;
diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
index 58f1983..22932e9 100644
--- a/src/cyclictest/cyclictest.c
+++ b/src/cyclictest/cyclictest.c
@@ -450,7 +450,8 @@ static void tracemark(char *fmt, ...)
 	va_start(ap, fmt);
 	len = vsnprintf(tracebuf, TRACEBUFSIZ, fmt, ap);
 	va_end(ap);
-	write(tracemark_fd, tracebuf, len);
+	if (write(tracemark_fd, tracebuf, len) < 0)
+		err_msg_n(errno, "WARN: could not write to tracebuf");
 }
 
 
@@ -463,7 +464,8 @@ static void tracing(int on)
 		case KV_26_LT24: prctl(0, 1); break;
 		case KV_26_33:
 		case KV_30:
-			write(trace_fd, "1", 1);
+			if (write(trace_fd, "1", 1) < 0)
+				err_msg_n(errno, "Could not set trace_fd");
 			break;
 		default:	 break;
 		}
@@ -473,7 +475,8 @@ static void tracing(int on)
 		case KV_26_LT24: prctl(0, 0); break;
 		case KV_26_33:
 		case KV_30:
-			write(trace_fd, "0", 1);
+			if (write(trace_fd, "0", 1) < 0)
+				err_msg_n(errno, "Could not set trace_fd");
 			break;
 		default:	break;
 		}
diff --git a/src/pmqtest/pmqtest.c b/src/pmqtest/pmqtest.c
index 75d5ee8..78eaa9c 100644
--- a/src/pmqtest/pmqtest.c
+++ b/src/pmqtest/pmqtest.c
@@ -210,7 +210,8 @@ void *pmqthread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					if (write(tracing_enabled, "0", 1) < 0)
+						err_msg_n(errno, "WARN: could write to tracing_enabled");
 					close(tracing_enabled);
 				} else
 					snprintf(par->error, sizeof(par->error),
diff --git a/src/ptsematest/ptsematest.c b/src/ptsematest/ptsematest.c
index a31c745..f777b38 100644
--- a/src/ptsematest/ptsematest.c
+++ b/src/ptsematest/ptsematest.c
@@ -137,7 +137,8 @@ void *semathread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					if (write(tracing_enabled, "0", 1) < 0)
+						err_msg_n(errno, "WARN: Could not enable tracing.");
 					close(tracing_enabled);
 				} else
 					snprintf(par->error, sizeof(par->error),
diff --git a/src/rt-migrate-test/rt-migrate-test.c b/src/rt-migrate-test/rt-migrate-test.c
index d7b68dd..352a331 100644
--- a/src/rt-migrate-test/rt-migrate-test.c
+++ b/src/rt-migrate-test/rt-migrate-test.c
@@ -44,7 +44,7 @@
 #include <errno.h>
 #include <sched.h>
 #include <pthread.h>
-
+#include "error.h"
 #define gettid() syscall(__NR_gettid)
 
 int nr_tasks;
@@ -87,7 +87,8 @@ static void ftrace_write(const char *fmt, ...)
 	n = vsnprintf(buff, BUFSIZ, fmt, ap);
 	va_end(ap);
 
-	write(mark_fd, buff, n);
+	if (write(mark_fd, buff, n) < 0)
+		err_msg_n(errno, "WARN: Could not write to trace_marker.");
 }
 
 #define nano2sec(nan) (nan / 1000000000ULL)
diff --git a/src/sigwaittest/sigwaittest.c b/src/sigwaittest/sigwaittest.c
index 91fcdaa..abeaa35 100644
--- a/src/sigwaittest/sigwaittest.c
+++ b/src/sigwaittest/sigwaittest.c
@@ -36,6 +36,7 @@
 #include <sys/time.h>
 #include <linux/unistd.h>
 #include <utmpx.h>
+#include "error.h"
 #include "rt-utils.h"
 #include "rt-get_cpu.h"
 
@@ -185,7 +186,8 @@ void *semathread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					if (write(tracing_enabled, "0", 1) < 0)
+						err_msg_n(errno, "WARN: Could not disable tracing.");
 					close(tracing_enabled);
 				} else
 					snprintf(par->error, sizeof(par->error),
@@ -378,7 +380,9 @@ int main(int argc, char *argv[])
 			fprintf(stderr, "Could not create shared memory\n");
 			return 1;
 		}
-		ftruncate(shmem, totalsize);
+		if (ftruncate(shmem, totalsize) < 0)
+			err_msg_n(errno, "WARN: Could not truncate file to %d bytes.", totalsize);
+
 		param = mmap(0, totalsize, PROT_READ|PROT_WRITE, MAP_SHARED,
 		    shmem, 0);
 		if (param == MAP_FAILED) {
diff --git a/src/svsematest/svsematest.c b/src/svsematest/svsematest.c
index eeb8285..9d4d2b9 100644
--- a/src/svsematest/svsematest.c
+++ b/src/svsematest/svsematest.c
@@ -191,7 +191,8 @@ void *semathread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					if (write(tracing_enabled, "0", 1))
+						err_msg_n(errno, "WARN: Could not write to tracing_enabled!");
 					close(tracing_enabled);
 				} else
 					snprintf(par->error, sizeof(par->error),
@@ -431,7 +432,11 @@ int main(int argc, char *argv[])
 			fprintf(stderr, "Could not create shared memory\n");
 			return 1;
 		}
-		ftruncate(shmem, totalsize);
+		if (ftruncate(shmem, totalsize) < 0) {
+			fprintf(stderr, "Could not truncate file to specified size (%d)\n", totalsize);
+			return 1;
+
+		}
 		param = mmap(0, totalsize, PROT_READ|PROT_WRITE, MAP_SHARED,
 		    shmem, 0);
 		if (param == MAP_FAILED) {
-- 
1.9.1

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