From 49c7900407514b072ef5ce01ee2d737659be0b84 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 8 Oct 2022 18:44:14 +0200
Subject: [PATCH] Add %m to userspace printf

%m as a format specifier is a nonstandard glibc extension, but I like it so I'm implementing it.
What it does is print the value of strerror(errno), without consuming any arguments to printf().
---
 apps/src/memeater.c      |  2 +-
 libs/libc/src/printf.cpp | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/apps/src/memeater.c b/apps/src/memeater.c
index d8e87306..761eb910 100644
--- a/apps/src/memeater.c
+++ b/apps/src/memeater.c
@@ -15,7 +15,7 @@ int main()
         printf("Allocating 4 MB of memory... %p\n", allocated);
         sleep(1);
     } while ((allocated = malloc(CHUNK)));
-    perror("malloc");
+    printf("Memory allocation failed: %m\n");
     printf("Press any key to restart.\n");
     return 1;
 }
\ No newline at end of file
diff --git a/libs/libc/src/printf.cpp b/libs/libc/src/printf.cpp
index 740cc394..31f9750f 100644
--- a/libs/libc/src/printf.cpp
+++ b/libs/libc/src/printf.cpp
@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <luna.h>
 #include <stdarg.h>
 #include <stddef.h>
@@ -251,6 +252,21 @@ static int internal_printf(const char* format, PutString put_string_callback, ss
                     if (buffer_insert_index == 1024) flush_buffer();
                     break;
                 }
+                case 'm': {
+                    const char* str = strerror(errno);
+                    while (strlen(str) > 1024)
+                    {
+                        flush_buffer();
+                        memcpy(buffer, str, 1024);
+                        str += 1024;
+                        buffer_insert_index = 1024;
+                    }
+                    if (buffer_insert_index + strlen(str) > 1024) flush_buffer();
+                    memcpy(buffer + buffer_insert_index, str, strlen(str));
+                    buffer_insert_index += strlen(str);
+                    if (buffer_insert_index == 1024) flush_buffer();
+                    break;
+                }
                 case 's': {
                     const char* str = va_arg(ap, const char*);
                     while (strlen(str) > 1024)