diff --git a/cfg/std.cfg b/cfg/std.cfg
index 99196138f..6c4affa0b 100644
--- a/cfg/std.cfg
+++ b/cfg/std.cfg
@@ -1,40 +1,42 @@
 <?xml version="1.0"?>
 <def>
   <function name="abort"><noreturn>true</noreturn></function>
-  <function name="abs"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/><not-bool/></arg></function>
-  <function name="acos"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="abs"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/><not-bool/></arg></function>
+  <function name="acos"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
   <function name="asctime">
-	  <noreturn>false</noreturn>
-	  <leak-ignore/>
-	  <arg nr="1"><not-uninit/></arg>
+    <use-retval/>
+    <noreturn>false</noreturn>
+    <leak-ignore/>
+    <arg nr="1"><not-uninit/></arg>
   </function>
   <function name="assert">
     <leak-ignore/>
   </function>
-  <function name="asin"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="atan"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="atan2"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
+  <function name="asin"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="atan"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="atan2"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
   <function name="atexit"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-null/></arg></function>
-  <function name="atof"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="atoi"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="atol"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="atoll"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="calloc"><noreturn>false</noreturn><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
-  <function name="ceil"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="atof"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="atoi"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="atol"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="atoll"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="calloc"><use-retval/><noreturn>false</noreturn><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
+  <function name="ceil"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
   <function name="clearerr">
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="clock"><noreturn>false</noreturn><leak-ignore/></function>
-  <function name="cos"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="cosh"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="cos"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="cosh"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
   <function name="ctime">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-uninit/></arg>
   </function>
-  <function name="difftime"><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
+  <function name="difftime"><use-retval/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
   <function name="div">
 	  <pure/>
 	  <noreturn>false</noreturn>
@@ -43,18 +45,20 @@
 	  <arg nr="2"><not-uninit/></arg>
   </function>
   <function name="exit"><noreturn>true</noreturn><arg nr="1"><not-uninit/></arg></function>
-  <function name="exp"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="fabs"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="exp"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="fabs"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
   <function name="fclose">
 	  <noreturn>false</noreturn>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="feof">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="ferror">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
@@ -79,9 +83,10 @@
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
-  <function name="floor"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="fmod"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
+  <function name="floor"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="fmod"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg><arg nr="2"><not-uninit/></arg></function>
   <function name="fopen">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
@@ -201,6 +206,7 @@
         <arg nr="4"><not-null/><not-uninit/></arg>
   </function>
   <function name="mblen">
+        <use-retval/>
         <noreturn>false</noreturn>
         <leak-ignore/>
         <arg nr="1"><not-uninit/></arg>
@@ -251,32 +257,34 @@
 		<arg nr="1"><not-uninit/></arg>
 		<arg nr="1"><not-null/><not-uninit/></arg>
   </function>
-  <function name="getenv"><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-null/><not-uninit/></arg></function>
+  <function name="getenv"><use-retval/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-null/><not-uninit/></arg></function>
   <function name="gets">
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/></arg>
   </function>
   <function name="gmtime">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
-  <function name="isalnum"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isalpha"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isblank"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="iscntrl"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isdigit"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isgraph"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="islower"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isprint"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="ispunct"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isspace"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isupper"> <pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="isxdigit"><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="labs">    <pure/><noreturn>false</noreturn><leak-ignore/>   <arg nr="1"><not-uninit/></arg></function>
-  <function name="llabs">   <pure/><noreturn>false</noreturn><leak-ignore/>   <arg nr="1"><not-uninit/></arg></function>
+  <function name="isalnum"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isalpha"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isblank"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="iscntrl"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isdigit"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isgraph"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="islower"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isprint"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="ispunct"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isspace"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isupper"> <use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="isxdigit"><use-retval/><pure/><noreturn>false</noreturn> <leak-ignore/>  <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="labs">    <use-retval/><pure/><noreturn>false</noreturn><leak-ignore/>   <arg nr="1"><not-uninit/></arg></function>
+  <function name="llabs">   <use-retval/><pure/><noreturn>false</noreturn><leak-ignore/>   <arg nr="1"><not-uninit/></arg></function>
   <function name="ldexp">
+       <use-retval/>
        <pure/>
        <noreturn>false</noreturn>
        <leak-ignore/>
@@ -284,6 +292,7 @@
        <arg nr="2"><not-uninit/></arg>
   </function>
   <function name="rand">
+       <use-retval/>
        <noreturn>false</noreturn>
        <leak-ignore/>
   </function>
@@ -311,17 +320,18 @@
 	  <leak-ignore/>
 	  <arg nr="1"><not-uninit/></arg>
   </function>
-  <function name="log"><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
-  <function name="log10"><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="log"><use-retval/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="log10"><use-retval/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
   <function name="longjmp">
        <noreturn>false</noreturn>
        <leak-ignore/>
        <arg nr="1"><not-uninit/></arg>
        <arg nr="2"><not-uninit/></arg>
   </function>
-  <function name="malloc"><noreturn>false</noreturn><arg nr="1"><not-uninit/></arg></function>
-  <function name="alloca"><noreturn>false</noreturn><arg nr="1"><not-uninit/></arg></function>
+  <function name="malloc"><use-retval/><noreturn>false</noreturn><arg nr="1"><not-uninit/></arg></function>
+  <function name="alloca"><use-retval/><noreturn>false</noreturn><arg nr="1"><not-uninit/></arg></function>
   <function name="memchr">
+        <use-retval/>
         <pure/>
         <noreturn>false</noreturn>
         <leak-ignore/>
@@ -330,6 +340,7 @@
         <arg nr="3"><not-bool/><valid>0:</valid></arg>
   </function>
   <function name="memcmp">
+        <use-retval/>
         <pure/>
         <noreturn>false</noreturn>
         <leak-ignore/>
@@ -364,6 +375,7 @@
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="modf">
+       <use-retval/>
        <noreturn>false</noreturn>
        <leak-ignore/>
        <arg nr="1"><not-uninit/></arg>
@@ -375,6 +387,7 @@
 	  <arg nr="1"><not-uninit/></arg>
   </function>
   <function name="pow">
+       <use-retval/>
        <pure/>
        <noreturn>false</noreturn>
        <leak-ignore/>
@@ -400,6 +413,7 @@
 	  <arg nr="any"><not-uninit/></arg>
   </function>
   <function name="bsearch">
+       <use-retval/>
        <pure/>
        <noreturn>false</noreturn>
        <leak-ignore/>
@@ -459,7 +473,7 @@
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
-  <function name="round"><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
+  <function name="round"><use-retval/><pure/><noreturn>false</noreturn><leak-ignore/><arg nr="1"><not-uninit/></arg></function>
   <function name="scanf">
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
@@ -513,18 +527,21 @@
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="strchr">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-uninit/></arg>
   </function>
   <function name="wcschr">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-uninit/></arg>
   </function>
   <function name="strcmp">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <pure/>
 	  <leak-ignore/>
@@ -532,6 +549,7 @@
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcscmp">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <pure/>
 	  <leak-ignore/>
@@ -559,11 +577,13 @@
 	  <arg nr="4"><not-null/><not-uninit/></arg>
   </function>
   <function name="strlen">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	</function>
   <function name="wcslen">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
@@ -590,6 +610,7 @@
 	  <arg nr="3"><not-bool/><valid>0:</valid></arg>
   </function>
   <function name="strncmp">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
@@ -597,6 +618,7 @@
 	  <arg nr="3"><not-bool/><valid>0:</valid></arg>
   </function>
   <function name="wcsncmp">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
@@ -604,18 +626,21 @@
 	  <arg nr="3"><not-bool/><valid>0:</valid></arg>
   </function>
   <function name="strstr">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcsstr">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="strspn">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
@@ -636,28 +661,33 @@
 	  <arg nr="3"><not-uninit/></arg>
   </function>
   <function name="wcsspn">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="strerror">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
   </function>
   <function name="strcspn">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcscspn">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcspbrk">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
@@ -671,24 +701,28 @@
 	  <arg nr="3"><not-uninit/></arg>
   </function>
   <function name="strcoll">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcscoll">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="strrchr">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="2"><valid>0:255</valid></arg>
   </function>
   <function name="strbprk">
+    <use-retval/>
     <noreturn>false</noreturn>
     <leak-ignore/>
     <pure/>
@@ -696,11 +730,13 @@
     <arg nr="2"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcsrchr">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="strtok">
+    <use-retval/>
     <noreturn>false</noreturn>
     <pure/>
     <leak-ignore/>
@@ -713,87 +749,101 @@
     </arg>
   </function>
   <function name="strtol">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
   <function name="strtof">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="strtod">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="strtold">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="strtoul">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
   <function name="strtoll">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
   <function name="strtoull">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/>
 	  </arg> <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
-  <function name="time"> <noreturn>false</noreturn> <leak-ignore/> </function>
+  <function name="time"> <use-retval/> <noreturn>false</noreturn> <leak-ignore/> </function>
   <function name="tmpnam"> <noreturn>false</noreturn> <leak-ignore/> <arg nr="1"></arg></function>
-  <function name="tmpfile"> <noreturn>false</noreturn> </function>
-  <function name="tolower"> <noreturn>false</noreturn> <leak-ignore/> <arg nr="1"><valid>0:255</valid></arg> </function>
-  <function name="toupper"> <noreturn>false</noreturn> <leak-ignore/> <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="tmpfile"> <use-retval/> <noreturn>false</noreturn> </function>
+  <function name="tolower"> <use-retval/> <noreturn>false</noreturn> <leak-ignore/> <arg nr="1"><valid>0:255</valid></arg> </function>
+  <function name="toupper"> <use-retval/> <noreturn>false</noreturn> <leak-ignore/> <arg nr="1"><valid>0:255</valid></arg> </function>
   <function name="va_arg">   <noreturn>false</noreturn> <leak-ignore/> </function>
   <function name="va_copy">  <noreturn>false</noreturn> <leak-ignore/> </function>
   <function name="va_end">   <noreturn>false</noreturn> <leak-ignore/> </function>
   <function name="va_start"> <noreturn>false</noreturn> <leak-ignore/> </function>
   <function name="wcstof">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcstod">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcstold">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
   </function>
   <function name="wcstol">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
-	  <arg nr="1"><not-null/><not-uninit/></arg>	
+	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
   <function name="wcstoll">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
   <function name="wcstoul">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
 	  <arg nr="3"><valid>0,2:36</valid></arg>
   </function>
   <function name="wcstoull">
+    <use-retval/>
 	  <noreturn>false</noreturn>
 	  <leak-ignore/>
 	  <arg nr="1"><not-null/><not-uninit/></arg>
diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index 3a7ab9b37..79eefaedb 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -2740,3 +2740,31 @@ void CheckOther::varFuncNullUBError(const Token *tok)
                 "    return 0;\n"
                 "}");
 }
+
+//---------------------------------------------------------------------------
+// Check for ignored return values.
+//---------------------------------------------------------------------------
+void CheckOther::checkReturnIgnoredReturnValue()
+{
+    if (!_settings->isEnabled("warning"))
+        return;
+
+    const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
+    const std::size_t functions = symbolDatabase->functionScopes.size();
+    for (std::size_t i = 0; i < functions; ++i) {
+        const Scope * scope = symbolDatabase->functionScopes[i];
+        for (const Token* tok = scope->classStart; tok != scope->classEnd; tok = tok->next()) {
+            if (!Token::Match(tok, "%var% ("))
+                continue;
+
+            if (!tok->next()->astParent() && _settings->library.useretval.find(tok->str()) != _settings->library.useretval.end())
+                ignoredReturnValueError(tok, tok->str());
+        }
+    }
+}
+
+void CheckOther::ignoredReturnValueError(const Token* tok, const std::string& function)
+{
+    reportError(tok, Severity::warning, "ignoredReturnValue",
+                "Return value of function " + function + "() is not used.", false);
+}
diff --git a/lib/checkother.h b/lib/checkother.h
index f45d08425..111fa9919 100644
--- a/lib/checkother.h
+++ b/lib/checkother.h
@@ -73,6 +73,7 @@ public:
         checkOther.checkVarFuncNullUB();
         checkOther.checkNanInArithmeticExpression();
         checkOther.checkCommaSeparatedReturn();
+        checkOther.checkReturnIgnoredReturnValue();
     }
 
     /** @brief Run checks against the simplified token list */
@@ -229,6 +230,9 @@ public:
     /** @brief %Check for using of comparison functions evaluating always to true or false. */
     void checkComparisonFunctionIsAlwaysTrueOrFalse();
 
+    /** @brief %Check for ignored return values. */
+    void checkReturnIgnoredReturnValue();
+
 private:
     // Error messages..
     void checkComparisonFunctionIsAlwaysTrueOrFalseError(const Token* tok, const std::string &strFunctionName, const std::string &varName, const bool result);
@@ -282,6 +286,7 @@ private:
     void incompleteArrayFillError(const Token* tok, const std::string& buffer, const std::string& function, bool boolean);
     void varFuncNullUBError(const Token *tok);
     void commaSeparatedReturnError(const Token *tok);
+    void ignoredReturnValueError(const Token* tok, const std::string& function);
 
     void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings) const {
         CheckOther c(0, settings, errorLogger);
@@ -337,6 +342,7 @@ private:
         c.varFuncNullUBError(0);
         c.nanInArithmeticExpressionError(0);
         c.commaSeparatedReturnError(0);
+        c.ignoredReturnValueError(0, "malloc");
     }
 
     static std::string myName() {
@@ -361,6 +367,7 @@ private:
                // warning
                "* either division by zero or useless condition\n"
                "* memset() with a value out of range as the 2nd parameter\n"
+               "* return value of certain functions not used\n"
 
                // performance
                "* redundant data copying for const variable\n"
diff --git a/lib/library.cpp b/lib/library.cpp
index 6eb78b5de..27dde7a9d 100644
--- a/lib/library.cpp
+++ b/lib/library.cpp
@@ -163,6 +163,8 @@ Library::Error Library::load(const tinyxml2::XMLDocument &doc)
                     functionpure.insert(name); // a constant function is pure
                 } else if (functionnodename == "leak-ignore")
                     leakignore.insert(name);
+                else if (functionnodename == "use-retval")
+                    useretval.insert(name);
                 else if (functionnodename == "arg" && functionnode->Attribute("nr") != nullptr) {
                     const bool bAnyArg = strcmp(functionnode->Attribute("nr"),"any")==0;
                     const int nr = (bAnyArg) ? -1 : atoi(functionnode->Attribute("nr"));
diff --git a/lib/library.h b/lib/library.h
index f050df0c4..d02c2d005 100644
--- a/lib/library.h
+++ b/lib/library.h
@@ -123,6 +123,7 @@ public:
     std::set<std::string> leakignore;
     std::set<std::string> functionconst;
     std::set<std::string> functionpure;
+    std::set<std::string> useretval;
 
     bool isnoreturn(const std::string &name) const {
         std::map<std::string, bool>::const_iterator it = _noreturn.find(name);
diff --git a/test/testother.cpp b/test/testother.cpp
index e66ad08b1..afeff0035 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -33,9 +33,11 @@ public:
     }
 
 private:
-
+    Settings settings_std;
 
     void run() {
+        LOAD_LIB_2(settings_std.library, "std.cfg");
+
         TEST_CASE(emptyBrackets);
 
         TEST_CASE(zeroDiv1);
@@ -167,7 +169,9 @@ private:
 
         TEST_CASE(checkComparisonFunctionIsAlwaysTrueOrFalse);
 
-        TEST_CASE(integerOverflow) // #5895
+        TEST_CASE(integerOverflow); // #5895
+
+        TEST_CASE(testReturnIgnoredReturnValue);
     }
 
     void check(const char code[], const char *filename = nullptr, bool experimental = false, bool inconclusive = true, bool posix = false, bool runSimpleChecks=true, Settings* settings = 0) {
@@ -4174,14 +4178,10 @@ private:
               "}");
         ASSERT_EQUALS("", errout.str());
 
-        {
-            Settings settings;
-            LOAD_LIB_2(settings.library, "std.cfg");
-            check("void foo() {\n"
-                  "    if ((strcmp(a, b) == 0) || (strcmp(a, b) == 0)) {}\n"
-                  "}", "test.cpp", false, false, false, true, &settings);
-            ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:2]: (style) Same expression on both sides of '||'.\n", errout.str());
-        }
+        check("void foo() {\n"
+              "    if ((strcmp(a, b) == 0) || (strcmp(a, b) == 0)) {}\n"
+              "}", "test.cpp", false, false, false, true, &settings_std);
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:2]: (style) Same expression on both sides of '||'.\n", errout.str());
 
         check("void GetValue() { return rand(); }\n"
               "void foo() {\n"
@@ -4785,14 +4785,12 @@ private:
             "}");
         ASSERT_EQUALS("[test.cpp:4]: (error) Memory pointed to by 'p' is freed twice.\n", errout.str());
 
-        Settings settings;
-        LOAD_LIB_2(settings.library, "std.cfg");
         check(
             "void foo(char *p) {\n"
             "  free(p);\n"
             "  printf(\"Freed memory at location %x\", p);\n"
             "  free(p);\n"
-            "}", nullptr, false, false, false, true, &settings);
+            "}", nullptr, false, false, false, true, &settings_std);
         ASSERT_EQUALS("[test.cpp:4]: (error) Memory pointed to by 'p' is freed twice.\n", errout.str());
 
         check(
@@ -6260,6 +6258,28 @@ private:
               "}\n");
         ASSERT_EQUALS("", errout.str());
     }
+
+    void testReturnIgnoredReturnValue() {
+        check("void foo() {\n"
+              "    strcmp(a, b);\n"
+              "}", "test.cpp", false, false, false, true, &settings_std);
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Return value of function strcmp() is not used.\n", errout.str());
+
+        check("void foo() {\n"
+              "    return strcmp(a, b);\n"
+              "}", "test.cpp", false, false, false, true, &settings_std);
+        ASSERT_EQUALS("", errout.str());
+
+        check("void foo() {\n"
+              "    if(strcmp(a, b));\n"
+              "}", "test.cpp", false, false, false, true, &settings_std);
+        ASSERT_EQUALS("", errout.str());
+
+        check("void foo() {\n"
+              "    bool b = strcmp(a, b);\n"
+              "}", "test.cpp", false, false, false, true, &settings_std);
+        ASSERT_EQUALS("", errout.str());
+    }
 };
 
 REGISTER_TEST(TestOther)