From 2a52c22f36854e7c322c92adbee98555ad75dbd8 Mon Sep 17 00:00:00 2001
From: Alex Kotov <kotovalexarian@gmail.com>
Date: Sun, 27 Nov 2022 05:19:14 +0400
Subject: [PATCH] Implement libc callbacks (#112)

---
 libc/Makefile.am            |  1 +
 libc/include/Makefile.am    |  1 +
 libc/include/kernaux/libc.h | 26 +++++++++++++++++++++
 libc/include/stdlib.h       |  4 ++++
 libc/src/kernaux.c          | 17 ++++++++++++++
 libc/src/stdlib.c           | 46 +++++++++++++++++++++++++++++++++----
 6 files changed, 91 insertions(+), 4 deletions(-)
 create mode 100644 libc/include/kernaux/libc.h
 create mode 100644 libc/src/kernaux.c

diff --git a/libc/Makefile.am b/libc/Makefile.am
index acdfa47..dcee272 100644
--- a/libc/Makefile.am
+++ b/libc/Makefile.am
@@ -11,6 +11,7 @@ endif
 libc_la_SOURCES = \
 	src/ctype.c \
 	src/errno.c \
+	src/kernaux.c \
 	src/stdlib.c \
 	src/string.c
 
diff --git a/libc/include/Makefile.am b/libc/include/Makefile.am
index 3a76e8c..4a748cc 100644
--- a/libc/include/Makefile.am
+++ b/libc/include/Makefile.am
@@ -1,4 +1,5 @@
 nobase_include_HEADERS = \
+	kernaux/libc.h \
 	ctype.h \
 	errno.h \
 	inttypes.h \
diff --git a/libc/include/kernaux/libc.h b/libc/include/kernaux/libc.h
new file mode 100644
index 0000000..46ceb92
--- /dev/null
+++ b/libc/include/kernaux/libc.h
@@ -0,0 +1,26 @@
+#ifndef KERNAUX_INCLUDED_LIBC
+#define KERNAUX_INCLUDED_LIBC
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stddef.h>
+
+struct KernAux_Libc {
+    void (*abort)() __attribute__((noreturn));
+    void (*exit)(int status) __attribute__((noreturn));
+
+    void *(*calloc)(size_t nmemb, size_t size);
+    void  (*free)(void *ptr);
+    void *(*malloc)(size_t size);
+    void *(*realloc)(void *ptr, size_t size);
+};
+
+extern struct KernAux_Libc kernaux_libc;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 56e41db..18baf84 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -12,10 +12,14 @@ extern "C" {
 
 int atoi(const char *str);
 
+__attribute__((noreturn))
 void abort();
+__attribute__((noreturn))
 void exit(int status);
 
+void *calloc(size_t nmemb, size_t size);
 void free(void *ptr);
+void *malloc(size_t size);
 void *realloc(void *ptr, size_t size);
 
 #ifdef __cplusplus
diff --git a/libc/src/kernaux.c b/libc/src/kernaux.c
new file mode 100644
index 0000000..688c769
--- /dev/null
+++ b/libc/src/kernaux.c
@@ -0,0 +1,17 @@
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <kernaux/libc.h>
+
+#include <stddef.h>
+
+struct KernAux_Libc kernaux_libc = {
+    .abort = NULL,
+    .exit = NULL,
+
+    .calloc = NULL,
+    .free = NULL,
+    .malloc = NULL,
+    .realloc = NULL,
+};
diff --git a/libc/src/stdlib.c b/libc/src/stdlib.c
index 1959031..5d6a9ca 100644
--- a/libc/src/stdlib.c
+++ b/libc/src/stdlib.c
@@ -2,22 +2,60 @@
 #include "config.h"
 #endif
 
+#include <kernaux/libc.h>
+
 #include <ctype.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <string.h>
 
-// TODO: stub
-void exit(const int status __attribute__((unused)))
+void exit(const int status)
 {
-    for (;;);
+    // Custom implementation
+    kernaux_libc.exit(status);
 }
 
-// TODO: stub
 void abort()
 {
+    // Custom implementation
+    if (kernaux_libc.abort) kernaux_libc.abort();
+
+    // Default implementation
     exit(EXIT_FAILURE);
 }
 
+void *calloc(const size_t nmemb, const size_t size)
+{
+    // Custom implementation
+    if (kernaux_libc.calloc) return kernaux_libc.calloc(nmemb, size);
+
+    // Default implementation
+    const size_t total_size = nmemb * size;
+    if (!total_size) return NULL;
+    if (total_size / nmemb != size) return NULL;
+    void *const ptr = malloc(total_size);
+    if (ptr) memset(ptr, 0, total_size);
+    return ptr;
+}
+
+void free(void *const ptr)
+{
+    // Custom implementation
+    kernaux_libc.free(ptr);
+}
+
+void *malloc(const size_t size)
+{
+    // Custom implementation
+    return kernaux_libc.malloc(size);
+}
+
+void *realloc(void *const ptr, const size_t size)
+{
+    // Custom implementation
+    return kernaux_libc.realloc(ptr, size);
+}
+
 int atoi(const char *str)
 {
     while (isspace(*str)) ++str;