diff --git a/cfg/gnu.cfg b/cfg/gnu.cfg
index e5996593d..0dcc2c99c 100644
--- a/cfg/gnu.cfg
+++ b/cfg/gnu.cfg
@@ -28,7 +28,7 @@
   <function name="bswap_16">
     <noreturn>false</noreturn>
     <use-retval/>
-    <returnValue type="uint16_t"/>
+    <returnValue type="uint16_t">((arg1 &amp; 0xff00u) &gt;&gt; 8) | ((arg1 &amp; 0x00ffu) &lt;&lt; 8)</returnValue>
     <leak-ignore/>
     <const/>
     <arg nr="1" direction="in">
@@ -42,7 +42,7 @@
   <function name="bswap_32">
     <noreturn>false</noreturn>
     <use-retval/>
-    <returnValue type="uint32_t"/>
+    <returnValue type="uint32_t">((arg1 &amp; 0xff000000ul) &gt;&gt; 24) | ((arg1 &amp; 0x00ff0000ul) &gt;&gt; 8) | ((arg1 &amp; 0x0000ff00ul) &lt;&lt; 8) | ((arg1 &amp; 0x000000fful) &lt;&lt; 24)</returnValue>
     <leak-ignore/>
     <const/>
     <arg nr="1" direction="in">
@@ -56,7 +56,7 @@
   <function name="bswap_64">
     <noreturn>false</noreturn>
     <use-retval/>
-    <returnValue type="uint64_t"/>
+    <returnValue type="uint64_t">((arg1 &amp; 0xff00000000000000ull) &gt;&gt; 56) | ((arg1 &amp; 0x00ff000000000000ull) &gt;&gt; 40) | ((arg1 &amp; 0x0000ff0000000000ull) &gt;&gt; 24) | ((arg1 &amp; 0x000000ff00000000ull) &gt;&gt; 8) | ((arg1 &amp; 0x00000000ff000000ull) &lt;&lt; 8) | ((arg1 &amp; 0x0000000000ff0000ull) &lt;&lt; 24) | ((arg1 &amp; 0x000000000000ff00ull) &lt;&lt; 40) | ((arg1 &amp; 0x00000000000000ffull) &lt;&lt; 56)</returnValue>
     <leak-ignore/>
     <const/>
     <arg nr="1" direction="in">
diff --git a/test/cfg/gnu.c b/test/cfg/gnu.c
index cebdd6f01..7c660e4fb 100644
--- a/test/cfg/gnu.c
+++ b/test/cfg/gnu.c
@@ -153,6 +153,26 @@ void valid_code(int argInt1, va_list valist_arg, int * parg)
     void * p_mmap = mmap(NULL, 1, PROT_NONE, MAP_ANONYMOUS | MAP_SHARED, -1, 0);
     printf("%p", p_mmap);
     munmap(p_mmap, 1);
+
+    uint16_t i16_1 = 0, i16_2;
+    // cppcheck-suppress unreadVariable
+    i16_2 = __builtin_bswap16(i16_1++);
+    uint32_t i32_1 = 0, i32_2;
+    // cppcheck-suppress unreadVariable
+    i32_2 = __builtin_bswap32(i32_1++);
+    uint64_t i64_1 = 0, i64_2;
+    // cppcheck-suppress unreadVariable
+    i64_2 = __builtin_bswap64(i64_1++);
+    
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i16_1 /= bswap_16(0x1234) - 0x3412;
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i32_1 /= bswap_32(0x12345678) - 0x78563412;
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i64_1 /= bswap_64(0x023456789abcde0f) - 0x0fdebc9a78563402;
 }
 
 void ignoreleak(void)