[CStringSyntaxChecker] Check strlcat sizeof check

- Assuming strlcat is used with strlcpy we check as we can if the last argument does not equal os not larger than the buffer.
- Advising the proper usual pattern.

Reviewers: NoQ, george.karpenkov

Reviewed By: george.karpenkov

Differential Revision: https://reviews.llvm.org/D49722

llvm-svn: 339641

1 files changed, 17 insertions, 0 deletions

diff --git a/clang/test/Analysis/cstring-syntax.c b/clang/test/Analysis/cstring-syntax.c
index fe1253bedba..c6d36940605 100644
--- a/clang/test/Analysis/cstring-syntax.c
+++ b/clang/test/Analysis/cstring-syntax.c
@@ -7,6 +7,7 @@ typedef __SIZE_TYPE__ size_t;
 char  *strncat(char *, const char *, size_t);
 size_t strlen (const char *s);
 size_t strlcpy(char *, const char *, size_t);
+size_t strlcat(char *, const char *, size_t);
 
 void testStrncat(const char *src) {
   char dest[10];
@@ -33,3 +34,19 @@ void testStrlcpy(const char *src) {
   strlcpy(dest + 5, src, 5);
   strlcpy(dest + 5, src, 10); // expected-warning {{The third argument is larger than the size of the input buffer.}}
 }
+
+void testStrlcat(const char *src) {
+  char dest[10];
+  size_t badlen = 10;
+  size_t ulen;
+  strlcpy(dest, "aaaaa", sizeof("aaaaa") - 1);
+  strlcat(dest, "bbbb", (sizeof("bbbb") - 1) - sizeof(dest) - 1);
+  strlcpy(dest, "012345678", sizeof(dest));
+  strlcat(dest, "910", sizeof(dest)); // expected-warning {{The third argument allows to potentially copy more bytes than it should. Replace with the value  <size>  - strlen(dest) - 1 or lower}}
+  strlcpy(dest, "0123456789", sizeof(dest));
+  strlcat(dest, "0123456789", badlen); // expected-warning {{The third argument allows to potentially copy more bytes than it should. Replace with the value 'badlen' - strlen(dest) - 1 or lower}}
+  strlcat(dest, "0123456789", badlen - strlen(dest) - 1);
+  strlcat(dest, src, ulen);
+  strlcpy(dest, src, 5);
+  strlcat(dest + 5, src, badlen); // expected-warning {{The third argument allows to potentially copy more bytes than it should. Replace with the value 'badlen' - strlen(<destination buffer>) - 1 or lower}}
+}