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Patch out any instances of printf in upstream #663

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Merged
apoelstra merged 3 commits into from
Nov 15, 2023
Merged

Patch out any instances of printf in upstream #663

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51dab7a
vendor-libsecp: remove util.h patch
apoelstra Nov 1, 2023
942a0e5
build.rs: patch out any calls to `printf`
apoelstra Nov 1, 2023
7a0c60e
secp256k1-sys: patch out checked_malloc
apoelstra Nov 6, 2023
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7 changes: 6 additions & 1 deletion secp256k1-sys/build.rs
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Expand Up @@ -20,11 +20,16 @@ fn main() {
.include("depend/secp256k1/include")
.include("depend/secp256k1/src")
.flag_if_supported("-Wno-unused-function") // some ecmult stuff is defined but not used upstream
.flag_if_supported("-Wno-unused-parameter") // patching out printf causes this warning
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@Kixunil Kixunil Nov 2, 2023

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I think this can be solved more locally but I haven't used C for a while so I don't remember how.

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@apoelstra apoelstra Nov 2, 2023

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There's no standard C way to do it. Any specific compiler would have annotations but they wouldn't work for others. (Of course, flag_if_supported also not universal. But cc makes an effort to translate it for the common compilers.)

And in any case, if I wanted a more local solution, I'd just patch out the offending methods entirely :).

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@Kixunil Kixunil Nov 3, 2023

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I mean something like using (void)x works IIRC which can be used in the define. But I don't know how to apply it to multiple arguments.

.define("SECP256K1_API", Some(""))
.define("ENABLE_MODULE_ECDH", Some("1"))
.define("ENABLE_MODULE_SCHNORRSIG", Some("1"))
.define("ENABLE_MODULE_EXTRAKEYS", Some("1"))
.define("ENABLE_MODULE_ELLSWIFT", Some("1"));
.define("ENABLE_MODULE_ELLSWIFT", Some("1"))
// upstream sometimes introduces calls to printf, which we cannot compile
// with WASM due to its lack of libc. printf is never necessary and we can
// just #define it away.
.define("printf(...)", Some(""));
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@tcharding tcharding Nov 2, 2023 •
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I think we should only use this if the target is wasm ie., put it in:

    // WASM headers and size/align defines.
    if env::var("CARGO_CFG_TARGET_ARCH").unwrap() == "wasm32" {

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@tcharding tcharding Nov 2, 2023

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Also the -Wno-unused-paramater

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@apoelstra apoelstra Nov 2, 2023

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Why?

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@tcharding tcharding Nov 3, 2023

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Because there is a bug in cc::Build::flag_if_supported so we are getting loads of warnings. Well on my machine anyways.

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@tcharding tcharding Nov 8, 2023

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Why?

Did you mean why do I think we should put the .define on the wasm-only cc::Build or why the "Also the -Wno-unused-parameter? Ignore the second one, and for the first, I thought this because the code comment specifically mentions that this is a wasm problem so it seems logical to put it in the wasm-only place.

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@apoelstra apoelstra Nov 10, 2023

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I don't think it's wasm-only. It would be any linker that tries to resolve libc symbols before pruning unused code.


if cfg!(feature = "lowmemory") {
base_config.define("ECMULT_WINDOW_SIZE", Some("4")); // A low-enough value to consume negligible memory
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12 changes: 4 additions & 8 deletions secp256k1-sys/depend/secp256k1/src/util.h
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Expand Up @@ -8,9 +8,7 @@
#define SECP256K1_UTIL_H

#include "../include/secp256k1.h"
extern int rustsecp256k1_v0_9_0_ecdsa_signature_parse_compact(
const rustsecp256k1_v0_9_0_context *ctx,
rustsecp256k1_v0_9_0_ecdsa_signature *sig, const unsigned char *input64);

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
Expand Down Expand Up @@ -147,11 +145,9 @@ static const rustsecp256k1_v0_9_0_callback default_error_callback = {
#endif

static SECP256K1_INLINE void *checked_malloc(const rustsecp256k1_v0_9_0_callback* cb, size_t size) {
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@Kixunil Kixunil Nov 6, 2023

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Maybe delete it completely to ensure it's not called by accident?

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@apoelstra apoelstra Nov 6, 2023

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Then I would need to delete all the functions that call it, and so on, which is much more invasive.

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@Kixunil Kixunil Nov 6, 2023

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Sucks. Also I wonder how does it interact with the system library. Will anything break if it has different code?

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@apoelstra apoelstra Nov 6, 2023

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No. It's not an exposed function, it's only used internally.

void *ret = malloc(size);
if (ret == NULL) {
rustsecp256k1_v0_9_0_callback_call(cb, "Out of memory");
}
return ret;
(void) cb;
(void) size;
return NULL;
}

#if defined(__BIGGEST_ALIGNMENT__)
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14 changes: 9 additions & 5 deletions secp256k1-sys/depend/util.h.patch
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@@ -1,6 +1,10 @@
10c10,12
<
148,152c148,150
< void *ret = malloc(size);
< if (ret == NULL) {
< secp256k1_callback_call(cb, "Out of memory");
< }
< return ret;
---
> extern int secp256k1_ecdsa_signature_parse_compact(
> const secp256k1_context *ctx,
> secp256k1_ecdsa_signature *sig, const unsigned char *input64);
> (void) cb;
> (void) size;
> return NULL;