================
@@ -0,0 +1,95 @@
+// RUN: %check_clang_tidy %s bugprone-suspicious-fread-fwrite-return %t
+
+typedef decltype(sizeof(int)) size_t;
+
+struct FILE;
+extern "C" size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
+extern "C" size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE
*stream);
+
+void test_direct_comparison(FILE *fp, void *buf, size_t size) {
+ if (fwrite(buf, 1, size, fp) < -1) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:32: warning: return value of 'fwrite' is
an unsigned 'size_t'; this comparison is always false
[bugprone-suspicious-fread-fwrite-return]
+ // CHECK-FIXES: if (fwrite(buf, 1, size, fp) != size) {
+ }
+
+ if (fwrite(buf, 1, size, fp) >= -1) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:32: warning: return value of 'fwrite' is
an unsigned 'size_t'; this comparison is always true
+ // CHECK-FIXES: if (fwrite(buf, 1, size, fp) != size) {
+ }
+
+ if (fwrite(buf, 1, size, fp) <= 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:32: warning: suspicious comparison against
0; 'fwrite' returns an unsigned 'size_t', so comparing it with '<= 0' is
equivalent to comparing it with '== 0'. To detect short reads or writes,
compare against the 'nmemb' argument
+ // CHECK-FIXES: if (fwrite(buf, 1, size, fp) != size) {
+ }
+
+ if (0 >= fread(buf, 1, size, fp)) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: suspicious comparison against
0; 'fread' returns an unsigned 'size_t', so comparing it with '0 >=' is
equivalent to comparing it with '== 0'. To detect short reads or writes,
compare against the 'nmemb' argument
+ // CHECK-FIXES: if (size != fread(buf, 1, size, fp)) {
+ }
+
+ if (0 < fread(buf, 1, size, fp)) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: return value of 'fread' is an
unsigned 'size_t'; this comparison is always true
+ // CHECK-FIXES: if (size != fread(buf, 1, size, fp)) {
+ }
+}
+
+void test_discarded_result(FILE *fp, void *buf, size_t size) {
+ if (fread(buf, 1, size, fp) == 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: return value of 'fread' is
compared to 0; since 'nmemb' is not 1, partial reads or writes cannot be
handled. Compare against the 'nmemb' argument instead
+ // CHECK-FIXES: if (fread(buf, 1, size, fp) != size) {
+ }
+
+ if (fread(buf, 1, size, fp) != 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: return value of 'fread' is
compared to 0; since 'nmemb' is not 1, partial reads or writes cannot be
handled. Compare against the 'nmemb' argument instead
+ // CHECK-FIXES: if (fread(buf, 1, size, fp) != size) {
+ }
+
+ if (fread(buf, 1, size, fp) > 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: return value of 'fread' is
compared to 0; since 'nmemb' is not 1, partial reads or writes cannot be
handled. Compare against the 'nmemb' argument instead
+ // CHECK-FIXES: if (fread(buf, 1, size, fp) != size) {
+ }
+
+ // If nmemb is exactly 1, == 0 is safe because it's an all-or-nothing read
+ if (fread(buf, size, 1, fp) == 0) {
+ // No warning
+ }
+
+ // Streaming/EOF checks (like while(> 0)) are valid if not a direct
comparison (e.g., they assign or loop).
+ // However, this check only catches direct comparisons to avoid breaking
legitimate streaming loops.
+ while (fwrite(buf, 1, size, fp) > 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:35: warning: return value of 'fwrite' is
compared to 0; since 'nmemb' is not 1, partial reads or writes cannot be
handled. Compare against the 'nmemb' argument instead
+ // CHECK-FIXES: while (fwrite(buf, 1, size, fp) != size) {
+ }
+}
+
+void test_correct_handling(FILE *fp, void *buf, size_t size) {
+ if (fwrite(buf, 1, size, fp) != size) {
+ // No warning
+ }
+
+ if (fwrite(buf, 1, size, fp) < size) {
+ // No warning
+ }
+
+ size_t written = fwrite(buf, 1, size, fp);
+ if (written < size) {
+ // No warning
+ }
+
+ if (written <= 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: suspicious comparison against
0; 'fwrite' returns an unsigned 'size_t', so comparing it with '<= 0' is
equivalent to comparing it with '== 0'. To detect short reads or writes,
compare against the 'nmemb' argument
+ // CHECK-FIXES: if (written != size) {
+ }
+}
+
+#define SIZE 16
+
+void test_macro_handling(FILE *fp, void *buf) {
+ if (fwrite(buf, 1, SIZE, fp) <= 0) {
+ // CHECK-MESSAGES: :[[@LINE-1]]:32: warning: suspicious comparison against
0; 'fwrite' returns an unsigned 'size_t', so comparing it with '<= 0' is
equivalent to comparing it with '== 0'. To detect short reads or writes,
compare against the 'nmemb' argument
+ // CHECK-FIXES: if (fwrite(buf, 1, SIZE, fp) != SIZE) {
+ }
+}
+
+
----------------
zeyi2 wrote:
Nit: excessive newline.
https://github.com/llvm/llvm-project/pull/206359
_______________________________________________
cfe-commits mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
