curl_global_init_mem(3)

💅 curl_global_init_mem — the manual page, but make it make sense

okay so bestie, you're reading curl_global_init_mem(3), out of the Library Functions Manual — yes it's a man page, yes it's giving "ancient scroll", but trust me this one's actually kind of a serve 🔥

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✨ NAME ✨

curl_global_init_mem — global libcurl initialization, but with memory callbacks 💖 like, you're the one in charge of the memory now. main character energy fr.

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🎀 SYNOPSIS 🎀

#include <curl/curl.h>

CURLcode curl_global_init_mem(long flags,
                              curl_malloc_callback m,
                              curl_free_callback f,
                              curl_realloc_callback r,
                              curl_strdup_callback s,
                              curl_calloc_callback c);

yeah it's a lot of params. we'll get through it together 🫶

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🌸 DESCRIPTION 🌸

so this function does literally the same thing as curl_global_init(3) — no cap — with exactly one extra little treat: it lets your application set callbacks that replace the internal memory functions libcurl would otherwise use. you're basically handing libcurl your own little memory toolbox 🧰✨

ngl though, here's the part where you gotta pay attention: if you're using libcurl from multiple threads, or libcurl was built with the threaded resolver option, then your callback functions must be thread safe. and the threaded resolver is a super common build option to enable — and in some cases it's literally the default — so we strongly urge you to make your callbacks thread safe. like, please. for me. 😭

also, all callback arguments must be set to valid function pointers. no vibes-only submissions, actual pointers. and the prototypes for the given callbacks have to match these exactly:

• void *malloc_callback(size_t size); → to replace malloc()
• void free_callback(void *ptr); → to replace free()
• void *realloc_callback(void *ptr, size_t size); → to replace realloc()
• char *strdup_callback(const char *str); → to replace strdup()
• void *calloc_callback(size_t nmemb, size_t size); → to replace calloc()

and like, this function is otherwise the same as curl_global_init(3), so please go read that man page for the actual documentation, i'm not retyping it, i love you but no 💅

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💀 CAUTION 💀

okay so this is the "don't come crying to me" section. manipulating these gives the application considerable powers to severely screw things up for libcurl. take care. like, actually take care. this is not a drill 🙈

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🌈 PROTOCOLS 🌈

this functionality affects all supported protocols ⭐ iconic, honestly, no notes.

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🦋 EXAMPLE 🦋

extern void *malloc_cb(size_t);
extern void free_cb(void *);
extern void *realloc_cb(void *, size_t);
extern char *strdup_cb(const char *);
extern void *calloc_cb(size_t, size_t);

int main(void)
{
  curl_global_init_mem(CURL_GLOBAL_DEFAULT, malloc_cb,
                       free_cb, realloc_cb,
                       strdup_cb, calloc_cb);
}

look at that. five little callbacks and one CURL_GLOBAL_DEFAULT. slay 🌸

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💜 AVAILABILITY 💜

added in curl 7.12.0 — a genuine vintage moment, iykyk 🎀

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👑 RETURN VALUE 👑

this function returns a CURLcode indicating success or error, bestie.

• CURLE_OK (0) means everything was OK ✅
• non-zero means an error occurred, go check libcurl-errors(3)

and if CURLOPT_ERRORBUFFER(3) was set with curl_easy_setopt(3), there can be an error message stored in the error buffer when non-zero is returned. so the error will be sitting there waiting for you, ready to explain itself 🫶

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🌟 SEE ALSO 🌟

• curl_global_cleanup(3)
• curl_global_init(3)

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a gentle reminder before you go: this page shipped as part of libcurl, dated 2026-10-12, and it's filed under Library Functions Manual. that's the whole vibe check 💖 go be thread safe out there. ✨🎀🦋