Finish curious case of gebs

blog/curious-case-of-gebs.md

@@ -12,8 +12,9 @@ GEBS also includes a bunch of extra helper macros, which turn C into a language
 So one thing I've noticed is that nob.h is used alongside of [arena](https://github.com/tsoding/arena). If you look into the implementation
 you can see some things, which are somewhat redundant like \`arena_sprintf()\` or \`arena_da_append()\`, \`arena_sb_append_cstr()\` and so on...
 First of all, why is an arena library managing string builders and dynamic arrays? In my opinion it should be the other way around.
-A string builder should rather accept a generic allocator interface, which it can then utilize to get it's memory. In GEBS this is done
-via a \`Gebs_Allocator\` interface.
+A string builder should rather accept a generic allocator interface, which it can then utilize to get it's memory.
+Basically we supplement a dynamic structure with an allocator of choice.
+In GEBS this is done via a \`Gebs_Allocator\` interface.
 
 \`\`\`c
 typedef struct {
@@ -58,3 +59,82 @@ This is my version of the \`XXX_da_append()\` macro:
 This way a dynamic list can work with any kind of allocator - the default libc allocator, an arena or literally anything else.
 We're not tied to the libc allocator and then have to implement the same macro of all other allocators.
 
+### Defer macro
+
+Ever forgot to place a \`free()\` call on function exit or an \`fclose()\`? The defer macro comes to the rescue. Here's a short snippet:
+(Taken straight form the source code of this website btw.)
+
+\`\`\`c
+    cJSON *root = cJSON_CreateObject();
+    defer { cJSON_Delete(root); }
+
+    char *time = __TIME__;
+    uchar md5_buf[16];
+    md5String(time, md5_buf);
+    String_Builder sb = {0};
+    defer { sb_free(&sb); }
+    for (size_t i = 0; i < 16; i++) {
+        sb_append_nstr(&sb, fmt("%02x", md5_buf[i]));
+    }
+    sb_finish(&sb);
+
+    cJSON_AddItemToObject(root, "build_id", cJSON_CreateString(sb.items));
+
+    make_application_json(result, 200, root);
+\`\`\`
+
+If not for the \`defer { ... }\` macro, remebering when to free memory would have been quite hellish.
+Another example:
+
+\`\`\`c
+    NString_List env = {0};
+    defer { list_free(&env); }
+
+    String_Builder out = {0};
+    defer { sb_free(&out); }
+
+    char path[PATH_MAX] = {0};
+    if (!get_baked_resource_path("home.html", path, sizeof(path))) {
+        make_internal_server_error(result);
+        return;
+    }
+\`\`\`
+
+On \`return\` we'd have to **NOT FORGET** to add \`list_free()\` and \`sb_free()\`, but now that we have our defer,
+we can kind of shut the brain off and not concern ourselves with freeing the memory. We can be 100% sure it's going to
+be freed if we step into the return statement.
+
+The implementation is quite simple, actually
+
+\`\`\`
+#define defer defer__2(__COUNTER__)
+#define defer__2(X) defer__3(X)
+#define defer__3(X) defer__4(defer__id##X)
+#define defer__4(ID) auto void ID##func(char (*)[]); __attribute__((cleanup(ID##func))) char ID##var[0]; void ID##func(char (*ID##param)[])
+\`\`\`
+
+Source article: https://gustedt.wordpress.com/2025/01/06/simple-defer-ready-to-use/
+
+### compile_flags.txt
+
+Clang/LLVM docs: https://clang.llvm.org/docs/JSONCompilationDatabase.html
+
+I use clangd inside of my vim. Clangd can be configured via a json database compile_commands.json. It's quite complicated for GEBS in a sense
+that it uses the \`XX.c -> XX.o\` building pattern, while GEBS is focused more on unity builds (it's on the programmer to implement caching).
+Luckily, clangd can be configured via a simple and minimalistic config file - \`compile_flags.txt\`, which holds only compiler flags that
+are used to compile our C files. We can for eg. put some include paths in there and clangd will pick them up.
+
+In GEBS we can generate a \`compile_flags.txt\` file using a built-in macro:
+
+\`\`\`c
+    #define CFLAGS \\
+        "-I.", \\
+        "-I./some-lib", \\
+        "-Wall", \\
+        "-Wextra" \\
+
+    // #define other stuff like CC, LDFLAGS, SOURCES
+
+    make_compile_flags(CFLAGS); // Will output the file
+\`\`\`
+