Introduce some usage of the returns_nonnull attribute

This is currently limited to the ksh wrappers for malloc functions and
the sh_sub* functions used for creating subshell-local trees.

Author: JohnoKing

src/cmd/ksh93/include/defs.h

@@ -131,8 +131,6 @@ extern Sfio_t		*sh_sfeval(char*[]);
 extern void		sh_setmatch(const char*,ptrdiff_t,ptrdiff_t,ssize_t[],int);
 extern void             sh_scope(struct argnod*, int);
 extern Namval_t		*sh_scoped(Namval_t*);
-extern Dt_t		*sh_subtracktree(int);
-extern Dt_t		*sh_subfuntree(int);
 extern void		sh_subjobcheck(pid_t);
 extern int		sh_subsavefd(int);
 extern void		sh_subtmpfile(void);
@@ -144,6 +142,8 @@ extern void		sh_trim(char*);
 extern int		sh_type(const char*);
 extern void             sh_unscope(void);
 extern void		sh_clear_subshell_pwdfd(void);
+extern returns_nonnull Dt_t	*sh_subtracktree(int);
+extern returns_nonnull Dt_t	*sh_subfuntree(int);
 #if _lib_openat
     extern int		sh_diropenat(int,const char *);
     extern void		sh_pwdupdate(int);
@@ -154,12 +154,12 @@ extern void		sh_clear_subshell_pwdfd(void);
 #endif /* SHOPT_NAMESPACE */
 
 /* malloc related wrappers */
-extern void		*sh_malloc(size_t size);
-extern void		*sh_realloc(void *ptr, size_t size);
-extern void		*sh_calloc(size_t nmemb, size_t size);
-extern char		*sh_strdup(const char *s);
-extern void		*sh_memdup(const void *s, size_t n);
-extern char		*sh_getcwd(void);
+extern returns_nonnull void	*sh_malloc(size_t size);
+extern returns_nonnull void	*sh_realloc(void *ptr, size_t size);
+extern returns_nonnull void	*sh_calloc(size_t nmemb, size_t size);
+extern returns_nonnull char	*sh_strdup(const char *s);
+extern returns_nonnull void	*sh_memdup(const void *s, size_t n);
+extern char			*sh_getcwd(void);
 #define new_of(type,x)	((type*)sh_malloc(sizeof(type)+(x)))
 #define sh_newof(p,t,n,x)	((p)?(t*)sh_realloc((char*)(p),sizeof(t)*(n)+(x)):(t*)sh_calloc(1,sizeof(t)*(n)+(x)))
 

src/cmd/ksh93/sh/init.c

@@ -231,7 +231,7 @@ static noreturn void *nomemory(size_t s)
  * The following are wrapper functions for memory allocation.
  * These functions will error out if the allocation fails.
  */
-void *sh_malloc(size_t size)
+returns_nonnull void *sh_malloc(size_t size)
 {
 	void *cp;
 	cp = malloc(size);
@@ -240,7 +240,7 @@ void *sh_malloc(size_t size)
 	return cp;
 }
 
-void *sh_realloc(void *ptr, size_t size)
+returns_nonnull void *sh_realloc(void *ptr, size_t size)
 {
 	void *cp;
 	cp = realloc(ptr, size);
@@ -253,7 +253,7 @@ void *sh_realloc(void *ptr, size_t size)
 	return cp;
 }
 
-void *sh_calloc(size_t nmemb, size_t size)
+returns_nonnull void *sh_calloc(size_t nmemb, size_t size)
 {
 	void *cp;
 	cp = calloc(nmemb, size);
@@ -262,7 +262,7 @@ void *sh_calloc(size_t nmemb, size_t size)
 	return cp;
 }
 
-char *sh_strdup(const char *s)
+returns_nonnull char *sh_strdup(const char *s)
 {
 	char *dup;
 	dup = strdup(s);
@@ -271,7 +271,7 @@ char *sh_strdup(const char *s)
 	return dup;
 }
 
-void *sh_memdup(const void *s, size_t n)
+returns_nonnull void *sh_memdup(const void *s, size_t n)
 {
 	void *dup;
 	dup = memdup(s, n);

src/cmd/ksh93/sh/subshell.c

@@ -397,7 +397,7 @@ static void nv_restore(struct subshell *sp)
  * Return pointer to tracked alias tree (a.k.a. hash table, i.e. cached $PATH search results).
  * Create new one if in a subshell and one doesn't exist and 'create' is non-zero.
  */
-Dt_t *sh_subtracktree(int create)
+returns_nonnull Dt_t *sh_subtracktree(int create)
 {
 	struct subshell *sp = subshell_data;
 	if(create && sh.subshell && !sh.subshare)
@@ -416,7 +416,7 @@ Dt_t *sh_subtracktree(int create)
  * return pointer to function tree
  * create new one if in a subshell and one doesn't exist and create is non-zero
  */
-Dt_t *sh_subfuntree(int create)
+returns_nonnull Dt_t *sh_subfuntree(int create)
 {
 	struct subshell *sp = subshell_data;
 	if(create && sh.subshell && !sh.subshare)

src/lib/libast/features/common

@@ -9,6 +9,20 @@ std	noreturn note{ noreturn ok }end compile{
 	int main(void) { foo(); }
 }end
 
+tst	returns_nonnull - -Werror=attributes note{ returns_nonnull ok }end compile{
+	#include <stdlib.h>
+	__attribute__((__returns_nonnull__)) char *foobar(void)
+	{
+		return "barfoo";
+	}
+	int main(void)
+	{
+		if(foobar())
+			return 0;
+		return 1;
+	}
+}end
+
 cat{
 	#if __clang__
 	#pragma clang diagnostic ignored "-Wmissing-braces"
@@ -76,6 +90,12 @@ cat{
 	#endif /* _std_noreturn */
 
 	#include <stdbool.h>
+
+	#if _returns_nonnull
+	#define returns_nonnull __attribute__((__returns_nonnull__))
+	#else
+	#define returns_nonnull
+	#endif
 }end
 
 if	tst - note{ <stdarg.h>+<wchar.h> works }end compile{