bdlsb_fixedmemoutput: fix ubsan problem (#4825)

* bdlsb_fixedmemoutput: fix ubsan problem
bloomberg · Jul 16, 2024 · f36c72c · f36c72c
1 parent c676486
commit f36c72c
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Showing 2 changed files with 21 additions and 12 deletions.
diff --git a/groups/bdl/bdlsb/bdlsb_fixedmemoutput.h b/groups/bdl/bdlsb/bdlsb_fixedmemoutput.h
@@ -278,15 +278,16 @@ bsl::streamsize FixedMemOutput::sputn(const char      *s,
                                       bsl::streamsize  length)
 {
     BSLS_ASSERT(s);
-    BSLS_ASSERT(0 <= length);
 
-    pos_type current = d_pos;
-    d_pos += length;
-    if (d_pos > d_capacity) {
-        d_pos  = d_capacity;
-        length = static_cast<bsl::streamsize>(d_capacity - current);
+    length = bsl::min<bsl::streamsize>(length, d_capacity - d_pos);
+    if (0 < length) {
+        bsl::memcpy(d_buffer_p + static_cast<IntPtr>(d_pos), s, length);
+        d_pos += length;
+    }
+    else {
+        BSLS_ASSERT(0 == length);
     }
-    bsl::memcpy(d_buffer_p + static_cast<IntPtr>(current), s, length);
+
     return length;
 }
 

diff --git a/groups/bdl/bdlsb/bdlsb_fixedmemoutput.t.cpp b/groups/bdl/bdlsb/bdlsb_fixedmemoutput.t.cpp
@@ -723,10 +723,18 @@ int main(int argc, char **argv)
             // This segment verifies correct behavior across different initial
             // buffer states (buffer length x buffer contents.)
             for(size_t i = 0; i < DATA_LEN; ++i ) {
-                const int LINE      = DATA[i].d_line;
+                const TestData& data = DATA[i];
+                const int       LINE = data.d_line;
+                const int       CAP  = data.d_strCap;
+                const int       LEN  = data.d_length;
+                const int       RET  = data.d_returnVal;
+
+                if (veryVerbose) {
+                    P_(LINE);    P_(CAP);    P_(LEN);    P(RET);
+                }
 
-                char       *bytes = new char[DATA[i].d_strCap];
-                Obj         mSB(bytes, DATA[i].d_strCap);
+                char       *bytes = new char[CAP];
+                Obj         mSB(bytes, CAP);
                 const Obj&  SB = mSB;
 
                 for(unsigned j = 0; j < strlen(DATA[i].d_initCont); ++j ) {
@@ -739,8 +747,8 @@ int main(int argc, char **argv)
                 ASSERTV(LINE, 0 == strncmp(bytes,
                                            DATA[i].d_result,
                                            strlen(DATA[i].d_result )) );
-                ASSERTV(LINE, DATA[i].d_returnVal == retResult );
-                ASSERTV(LINE, DATA[i].d_length    == SB.length());
+                ASSERTV(LINE, RET == retResult );
+                ASSERTV(LINE, LEN == SB.length());
                 delete [] bytes;
             }
         }