libc: header documentation for supported functions

libc/include/errno.h

@@ -1,6 +1,9 @@
+/* errno.h: Error management header. */
+
 #ifndef _ERRNO_H
 #define _ERRNO_H
 
+/* The last error encountered after a call to a system or library function. */
 extern int errno;
 
 #include <luna/SystemError.h>

libc/include/stdio.h

@@ -1,3 +1,5 @@
+/* stdio.h: Standard input/output header. */
+
 #ifndef _STDIO_H
 #define _STDIO_H
 
@@ -36,7 +38,8 @@ extern "C"
     int vfprintf(FILE*, const char*, va_list);
     int sprintf(char*, const char*, ...);
 
-    int console_print(const char*);
+    /* Output a message to the console. */
+    int console_print(const char* msg);
 
 #ifdef __cplusplus
 }

libc/include/stdlib.h

@@ -32,22 +32,22 @@ extern "C"
 {
 #endif
 
-    /* Returns the absolute value of v. */
+    /* Return the absolute value of an integer. */
     int abs(int v);
 
-    /* Returns the absolute value of v. */
+    /* Return the absolute value of a long integer. */
     long labs(long v);
 
-    /* Returns the absolute value of v. */
+    /* Return the absolute value of a long long integer. */
     long long llabs(long long v);
 
-    /* Returns the result of dividing num by den, including the remainder. */
+    /* Return the result of dividing two integers, including the remainder. */
     div_t div(int num, int den);
 
-    /* Returns the result of dividing num by den, including the remainder. */
+    /* Return the result of dividing two long integers, including the remainder. */
     ldiv_t ldiv(long, long);
 
-    /* Returns the result of dividing num by den, including the remainder. */
+    /* Return the result of dividing two long long integers, including the remainder. */
     lldiv_t lldiv(long long, long long);
 
     void* malloc(size_t);
@@ -55,40 +55,40 @@ extern "C"
     void* realloc(void*, size_t);
     void free(void*);
 
-    /* Aborts the program without performing any normal cleanup. */
+    /* Abort the program without performing any normal cleanup. */
     __noreturn void abort();
 
-    /* Registers a handler to be run at normal program termination. */
+    /* Register a handler to be run at normal program termination. */
     int atexit(void (*func)(void));
 
-    /* Parses a decimal integer from the provided string. */
+    /* Parse a decimal integer from the a string. */
     int atoi(const char* s);
 
-    /* Parses a decimal integer from the provided string. */
+    /* Parse a decimal integer from the a string. */
     long atol(const char* s);
 
-    /* Parses a decimal integer from the provided string. */
+    /* Parse a decimal integer from the a string. */
     long long atoll(const char* s);
 
     double atof(const char*);
 
     double strtod(const char*, char**);
 
-    /* Parses an integer of the specified base from the string str, storing the first non-number character in endptr if
+    /* Parse an integer of the specified base from a string, storing the first non-number character in endptr if
      * nonnull. */
     long strtol(const char* str, char** endptr, int base);
 
-    /* Parses an unsigned integer of the specified base from the string str, storing the first non-number character in
+    /* Parse an unsigned integer of the specified base from a string, storing the first non-number character in
      * endptr if nonnull. */
     unsigned long strtoul(const char* str, char** endptr, int base);
 
     int rand();
     void srand(int);
 
-    /* Exits the program normally, performing any registered cleanup actions. */
+    /* Exit the program normally, performing any registered cleanup actions. */
     __noreturn void exit(int);
 
-    /* Exits the program abnormally, without performing any registered cleanup actions. */
+    /* Exit the program abnormally, without performing any registered cleanup actions. */
     __noreturn void _Exit(int);
 
     int system(const char*);

libc/include/string.h

@@ -1,3 +1,5 @@
+/* string.h: String manipulation header. */
+
 #ifndef _STRING_H
 #define _STRING_H
 
@@ -9,19 +11,37 @@ extern "C"
 {
 #endif
 
+    /* Copy n bytes of memory from src to dest. */
     void* memcpy(void* dest, const void* src, size_t n);
+
+    /* Set n bytes of memory to the character c. */
     void* memset(void* buf, int c, size_t n);
+
+    /* Compare n bytes of two memory locations. */
     int memcmp(const void* a, const void* b, size_t n);
+
+    /* Copy n bytes of memory from src to dest, where src and dest may overlap. */
     void* memmove(void* dest, const void* src, size_t n);
+
+    /* Return the length of a null-terminated string. */
     size_t strlen(const char* str);
 
+    /* Compare two null-terminated strings. */
     int strcmp(const char* a, const char* b);
+
+    /* Copy the null-terminated string src into dest. Should be avoided to prevent buffer overflow attacks. */
     __deprecated char* strcpy(char* dest, const char* src);
+
+    /* Concatenate the null-terminated string src onto dest. Should be avoided to prevent buffer overflow attacks. */
     __deprecated char* strcat(char* dest, const char* src);
+
+    /* Return a pointer to the first occurrence of the character c in str, or NULL if it could not be found. */
     char* strchr(const char* str, int c);
 
+    /* Return a heap-allocated copy of a string. */
     char* strdup(const char* str);
 
+    /* Return the human-readable description of an error number. */
     char* strerror(int errnum);
 
 #ifdef __cplusplus

libc/include/unistd.h

@@ -1,6 +1,11 @@
+/* unistd.h: POSIX constants and functions. */
+
 #ifndef _UNISTD_H
 #define _UNISTD_H
 
+#define __need_NULL
+#include <stddef.h>
+
 #include <stdint.h>
 #include <sys/types.h>
 
@@ -16,7 +21,8 @@ extern "C"
     int execve(const char*, char* const*, char* const*);
     int execvp(const char*, char* const*);
 
-    long syscall(long, ...);
+    /* Calls the operating system kernel for a specific service. */
+    long syscall(long num, ...);
 
 #ifdef __cplusplus
 }