libc: Add mktemp() and mkdtemp(), along with a test for mktemp

libs/libc/include/stdlib.h

@@ -120,7 +120,10 @@ extern "C"
     size_t mbstowcs(wchar_t* dest, const char* src,
                     size_t n); // Not implemented.
 
-    char* mktemp(char* base); // Not implemented.
+    /* Generate a unique filename from the template string str. The last 6 bytes of str must be 'XXXXXX', and they will
+     * be replaced with random characters. This function is deprecated due to race conditions; between the name being
+     * generated and creating a file with that name, that filename could have already been used. */
+    __lc_is_deprecated char* mktemp(char* str);
 
 #ifdef __cplusplus
 }

libs/libc/src/stdlib.cpp

@@ -2,6 +2,8 @@
 #include <luna.h>
 #include <luna/syscall.h>
 #include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -188,8 +190,52 @@ extern "C"
         NOT_IMPLEMENTED("mbstowcs");
     }
 
-    char* mktemp(char*)
+    static void gentemp(char* startptr)
     {
-        NOT_IMPLEMENTED("mktemp");
+        for (int i = 0; i < 6; i++)
+        {
+            startptr[i] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890"[rand() % 63];
+        }
+    }
+
+    char* mktemp(char* str)
+    {
+        size_t len = strlen(str);
+        if (len < 6)
+        {
+            errno = EINVAL;
+            return NULL;
+        }
+        char* startptr = str + (len - 6);
+        if (strncmp(startptr, "XXXXXX", 6))
+        {
+            errno = EINVAL;
+            return NULL;
+        }
+        do {
+            gentemp(startptr);
+        } while (access(str, F_OK) == 0);
+        return str;
+    }
+
+    char* mkdtemp(char* str)
+    {
+        size_t len = strlen(str);
+        if (len < 6)
+        {
+            errno = EINVAL;
+            return NULL;
+        }
+        char* startptr = str + (len - 6);
+        if (strncmp(startptr, "XXXXXX", 6))
+        {
+            errno = EINVAL;
+            return NULL;
+        }
+        do {
+            gentemp(startptr);
+        } while (mkdir(str, 0700) < 0 && errno == EEXIST);
+        if (errno) return NULL;
+        return str;
     }
 }

tests/libc/Makefile

@@ -4,7 +4,7 @@ DESTDIR := $(LUNA_ROOT)/initrd/bin
 build:
 	@mkdir -p $(TESTDIR)/bin
 	$(LUNA_ROOT)/tools/sync-libc.sh
-	$(CC) $(TESTDIR)/string.c $(TESTDIR)/stdlib.c $(TESTDIR)/Test.c -I$(LUNA_ROOT)/tests -o $(TESTDIR)/bin/test-libc -Wall -Wextra -Wno-stringop-overread -Werror
+	$(CC) $(TESTDIR)/string.c $(TESTDIR)/stdlib.c $(TESTDIR)/Test.c -I$(LUNA_ROOT)/tests -o $(TESTDIR)/bin/test-libc -Wall -Wextra -Wno-deprecated-declarations -Wno-stringop-overread -Werror
 
 install:
 	$(LUNA_ROOT)/tools/clean.sh

tests/libc/Test.c

@@ -24,6 +24,7 @@ DEFINE_TEST(atoll);
 DEFINE_TEST(srand);
 DEFINE_TEST(malloc);
 DEFINE_TEST(calloc);
+DEFINE_TEST(mktemp);
 
 int main()
 {
@@ -51,4 +52,5 @@ int main()
     RUN_TEST(srand);
     RUN_TEST(malloc);
     RUN_TEST(calloc);
+    RUN_TEST(mktemp);
 }

tests/libc/stdlib.c

@@ -1,5 +1,7 @@
 #include "Test.h"
 #include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 DEFINE_TEST(atoi)
 {
@@ -136,5 +138,29 @@ DEFINE_TEST(calloc)
 
     free(ptr);
 
+    TEST_SUCCESS();
+}
+
+DEFINE_TEST(mktemp)
+{
+    START_TEST(mktemp);
+
+    char template[] = "/tmp/file.XXXXXX";
+
+    const char* template2 = "/tmp/file.XXXXXX";
+
+    char* ptr = mktemp(template);
+
+    EXPECT_NOT_EQ(ptr, NULL); // mktemp only fails if we give it an invalid template.
+
+    int rc = access(ptr, F_OK);
+
+    EXPECT_NOT_EQ(rc, 0); // FIXME: This could actually happen, since that's why mktemp is deprecated. 
+                          // Another process could create the file between generating the name and actually using it.
+
+    rc = strcmp(ptr, template2);
+
+    EXPECT_NOT_EQ(rc, 0);
+
     TEST_SUCCESS();
 }