diff --git a/blog/curious-case-of-gebs.md b/blog/curious-case-of-gebs.md index 4f7895a..534c184 100644 --- a/blog/curious-case-of-gebs.md +++ b/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 +\`\`\` +