apps/examples/nsh: Add logic to automatically register an application symbol table as part of NSH initialization.

examples/nsh/Kconfig

@@ -13,6 +13,23 @@ config EXAMPLES_NSH
 
 if EXAMPLES_NSH
 
+config EXAMPLES_NSH_SYMTAB
+	bool "Register symbol table"
+	default n
+	depends on LIBC_EXECFUNCS && LIB_BOARDCTL && !EXECFUNCS_HAVE_SYMTAB
+	select BOARDCTL_APP_SYMTAB
+	---help---
+		Enable logic to automatically register an application symbol table
+		as part of NSH initialization.  If enabled, then application logic
+		must provide the following:
+
+			const struct symtab_s g_exports[];
+			const int g_nexports;
+
+		Where g_exports is the name of the exported application symbol table
+		and g_nexports holds the number of entries in the application symbol
+		table.
+
 config EXAMPLES_NSH_PROGNAME
 	string "Program name"
 	default "nsh"

examples/nsh/nsh_main.c

@@ -79,8 +79,17 @@
 #  undef HAVE_DUMMY_SYMTAB
 #endif
 
-#if defined(CONFIG_FS_BINFS) && !defined(HAVE_DUMMY_SYMTAB)
+/* If we are going to use the application symbol table, then suppress
-#  warning "Prequisites not met for BINFS dummy symbol table"
+ * the dummy symbol table.
+ */
+
+#ifdef CONFIG_EXAMPLES_NSH_SYMTAB
+#  undef HAVE_DUMMY_SYMTAB
+#endif
+
+#if defined(CONFIG_FS_BINFS) && !defined(HAVE_DUMMY_SYMTAB) && \
+   !defined(CONFIG_EXAMPLES_NSH_SYMTAB)
+#  warning "Prequisites not met for BINFS symbol table"
 #endif
 
 /* C++ initialization requires CXX initializer support */
@@ -109,7 +118,7 @@
  * Private Data
  ****************************************************************************/
 
-#ifdef HAVE_DUMMY_SYMTAB
+#if defined(HAVE_DUMMY_SYMTAB)
 /* If posix_spawn() is enabled as required for CONFIG_NSH_FILE_APPS, then
  * a symbol table is needed by the internals of posix_spawn().  The symbol
  * table is needed to support ELF and NXFLAT binaries to dynamically link to
@@ -120,7 +129,13 @@
  * you want to support ELF or NXFLAT binaries!
  */
 
-static const struct symtab_s CONFIG_EXECFUNCS_SYMTAB[1];  /* Wasted memory! */
+static const struct symtab_s g_dummy_symtab[1];  /* Wasted memory! */
+
+#elif defined(CONFIG_EXAMPLES_NSH_SYMTAB)
+
+extern const struct symtab_s g_exports[];
+extern const int g_nexports;
+
 #endif
 
 /****************************************************************************
@@ -137,7 +152,7 @@ int main(int argc, FAR char *argv[])
 int nsh_main(int argc, char *argv[])
 #endif
 {
-#ifdef HAVE_DUMMY_SYMTAB
+#if defined(HAVE_DUMMY_SYMTAB) || defined (CONFIG_EXAMPLES_NSH_SYMTAB)
   struct boardioc_symtab_s symdesc;
 #endif
   int exitval = 0;
@@ -149,11 +164,18 @@ int nsh_main(int argc, char *argv[])
   up_cxxinitialize();
 #endif
 
-#ifdef HAVE_DUMMY_SYMTAB
+#if defined(HAVE_DUMMY_SYMTAB) || defined (CONFIG_EXAMPLES_NSH_SYMTAB)
+#if defined(HAVE_DUMMY_SYMTAB)
   /* Make sure that we are using our symbol table */
 
   symdesc.symtab   = (FAR struct symtab_s *)g_dummy_symtab; /* Discard 'const' */
   symdesc.nsymbols = 0;
+
+#else  /* if defined(CONFIG_EXAMPLES_NSH_SYMTAB) */
+  symdesc.symtab   = (FAR struct symtab_s *)g_exports; /* Discard 'const' */
+  symdesc.nsymbols = g_nexports;
+#endif
+
   (void)boardctl(BOARDIOC_APP_SYMTAB, (uintptr_t)&symdesc);
 #endif