A command line tool and library for transferring data with URL syntax, supporting DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, POP3, POP3S, RTMP, RTMPS, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS and WSS. libcurl offers a myriad of powerful features
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Viktor Szakats 66ad54e46b
cmake: add CURL_DROP_UNUSED option to reduce binary sizes
To enable known linker options dropping unused, dead, code and data from
the executables built.

Useful to reduce binary sizes for curl, libcurl shared lib and apps
linking static libcurl. It's effective on both "unity" and non-unity
builds. Aligning "unity" build sizes with default, non-unity ones.

Supported platforms: Apple, MSVC, llvm/clang and GCC on all tested
platforms: Linux, BSDs, Windows, MSYS2/Cygwin, Android, MS-DOS.

Notes:
- Static libraries grow 20-30% with non-Apple toolchains.
  This effect is controlled by separate, optional compiler flags on
  non-Apple. This patch enables them automatically for public binaries
  (libcurl and curl tool), and leaves them off for internal/test ones.
- MSVC enables this option by default for 'Release' configurations.
  The curl build option has no effect on it.
- Observed effect on VS2010 is negligible. VS2012+ is recommended.
- Works with LTO, Fil-C.
- No observed/conclusive effect on build speed.
- On Windows with clang/gcc (mingw-w64/MSYS2/Cygwin) it also enables
  `-fno-asynchronous-unwind-tables` as a workaround to make
  the toolchain options actually work.
  Ref: https://sourceware.org/bugzilla/show_bug.cgi?id=11539
  Thanks-to: Andarwinux

Also:
- GHA: enable in Linux and MinGW jobs to test it. Size changes:

  - linux aws-lc H3:
    curl: 2000000 -> 1937152, libcurl.a: 2065724 -> 2716532 bytes
  - macos clang HTTP-only:
    curl: 1364376 -> 128799 bytes, libcurl.a: unchanged
  - macos llvm MultiSSL:
    curl: 410056 -> 405720, libcurl.dylib: 1350336 -> 1348480 bytes
  - mingw schannel c-ares U:
    curl: 1588736 -> 1507328, libcurl-d.a: 3322040 -> 3884746 bytes
    bld: 34 -> 35MB

- GHA: enable in MSVC and Apple jobs to reduce disk footprint, with no
  obvious downside. Size changes:

  - AppVeyor CI VS2019:
    curl: 2339840 -> 1295872, libcurl-d.dll: 3155968 -> 1900544 bytes
    bld: 161 -> 97MB
  - AppVeyor CI VS2022 clang-cl:
    curl: 2933248 -> 2332160, libcurl-d.lib: 4762688 -> 5511330 bytes
    bld: 133 -> 121MB
  - AppVeyor CI VS2022 HTTP-only:
    curl: 3514368 -> 2177024, libcurl-d.lib: 2538420 -> 3151740 bytes
    bld: 137 -> 83MB
  - GHA intel:
    curl: 2629120 -> 2023424, libcurl-d.lib: 4366652 -> 5350670 bytes
    bld: 86 -> 69MB
  - GHA arm64:
    curl: 2832896 -> 2063872, libcurl-d.lib: 4690616 -> 5597250 bytes
    bld: 82 -> 66MB

Refs:
https://maskray.me/blog/2021-02-28-linker-garbage-collection
https://web.archive.org/web/20110811230637/msdn.microsoft.com/en-us/library/bxwfs976.aspx (VS2010)
https://learn.microsoft.com/cpp/build/reference/opt-optimizations
https://learn.microsoft.com/cpp/build/reference/gy-enable-function-level-linking

Closes #20357
2026-01-22 17:08:20 +01:00
.circleci runtests: detect bad libssh differently for test 1459 (fixing CircleCI libssh job) 2025-11-16 23:28:44 +01:00
.github cmake: add CURL_DROP_UNUSED option to reduce binary sizes 2026-01-22 17:08:20 +01:00
CMake build: update to not need _CRT_NONSTDC_NO_DEPRECATE with MSVC 2026-01-20 23:19:54 +01:00
docs cmake: add CURL_DROP_UNUSED option to reduce binary sizes 2026-01-22 17:08:20 +01:00
include build: merge TrackMemory (CURLDEBUG) into debug-enabled option 2026-01-19 18:43:17 +01:00
lib cmake: add CURL_DROP_UNUSED option to reduce binary sizes 2026-01-22 17:08:20 +01:00
LICENSES krb5: drop support for Kerberos FTP 2025-09-20 23:58:28 +02:00
m4 build: drop global suppression of -Wformat-nonliteral, fix fallouts 2026-01-20 12:38:02 +01:00
projects tidy-up: miscellaneous 2026-01-20 12:37:56 +01:00
scripts build: update to not need _CRT_NONSTDC_NO_DEPRECATE with MSVC 2026-01-20 23:19:54 +01:00
src cmake: add CURL_DROP_UNUSED option to reduce binary sizes 2026-01-22 17:08:20 +01:00
tests build: fully omit verbose strings and code when disabled 2026-01-21 13:18:35 +01:00
.dir-locals.el copyright: update all copyright lines and remove year ranges 2023-01-03 09:19:21 +01:00
.editorconfig .editorconfig: add 2025-09-02 08:36:40 +02:00
.git-blame-ignore-revs copyright: update all copyright lines and remove year ranges 2023-01-03 09:19:21 +01:00
.gitattributes winbuild: MS-DOS batch tidy-ups 2024-07-02 19:26:15 +02:00
.gitignore build: drop the winbuild build system 2025-09-20 01:20:25 +02:00
.mailmap REUSE: add copyright header to two files 2025-11-03 16:08:52 +01:00
acinclude.m4 windows: add build option to use the native CA store 2026-01-17 19:18:52 +01:00
appveyor.sh cmake: add CURL_DROP_UNUSED option to reduce binary sizes 2026-01-22 17:08:20 +01:00
appveyor.yml appveyor: simplify job configuration 2026-01-21 19:34:12 +01:00
buildconf copyright: update all copyright lines and remove year ranges 2023-01-03 09:19:21 +01:00
CHANGES.md CHANGES: fix typo in filename 2026-01-01 12:20:10 +01:00
CMakeLists.txt cmake: add CURL_DROP_UNUSED option to reduce binary sizes 2026-01-22 17:08:20 +01:00
configure.ac tidy-up: miscellaneous 2026-01-20 12:37:56 +01:00
COPYING COPYING: bump copyright year range to 1996 - 2026 2026-01-08 23:19:44 +01:00
curl-config.in autotools: tidy-up if expressions 2025-12-10 22:29:19 +01:00
Dockerfile Dockerfile: update debian:bookworm-slim Docker digest to d5d3f9c 2025-12-31 12:22:53 +01:00
GIT-INFO.md REUSE: add copyright header to two files 2025-11-03 16:08:52 +01:00
libcurl.pc.in configure: do not echo most inherited LDFLAGS to config files 2024-11-14 09:55:45 +01:00
Makefile.am tidy-up: miscellaneous 2026-01-15 13:06:13 +01:00
README FAQ/TODO/KNOWN_BUGS: convert to markdown 2025-12-09 10:52:56 +01:00
README.md tidy-up: URLs 2025-12-09 00:19:10 +01:00
RELEASE-NOTES RELEASE-NOTES: synced 2026-01-20 16:01:16 +01:00
renovate.json renovate: try to disable GitHub Actions updates differently 2025-12-14 09:17:08 +01:00
REUSE.toml REUSE: drop broken reference to MAIL-ETIQUETTE 2026-01-19 07:48:15 +01:00
SECURITY.md docs: Clarify OpenSSF Best Practices vs Scorecard 2024-08-22 11:50:20 +02:00

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curl is a command-line tool for transferring data from or to a server using URLs. It supports these protocols: DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, POP3, POP3S, RTMP, RTMPS, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS and WSS.

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