Re: CURLOPT_ACCEPT_ENCODING not working (help)

From: Ray Satiro via curl-library <curl-library_at_cool.haxx.se>
Date: Fri, 5 Feb 2021 15:48:22 -0500

On 2/4/2021 10:07 AM, Adrián Gimeno Balaguer via curl-library wrote:
>
> I’m using a self built libcurl shared library for embedded use in a
> C++ application. In the attempt of requesting it to automatically
> decompress response data from a remote server of interest by using a
> line like the following in my request setup:
>
> curl_easy_setopt(mpCURL, CURLOPT_ACCEPT_ENCODING, "gzip");
>
> The returned data seems to remain compressed. I enabled the
> CURLOPT_HEADER option and can see that the server returns positive
> Content-Lengths, with few non-human readable characters in the body
> content. To be clear, removing the CURLOPT_ACCEPT_ENCODING option
> doesn’t make any difference.
>
> The libcurl library compilation is done in a custom automated CI/CD in
> the cloud which also compiles OpenSSL and ZLib as shared libraries in
> separate pipelines, with libcurl pipeline pulling from the master
> branch (from official libcurl’s repo) and a compilation script like
> the following:
>
> cmake -Bbuild -DBUILD_SHARED_LIBS=OFF -DCMAKE_BUILD_TYPE=MinSizeRel
> -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCURL_DISABLE_COOKIES=ON
> -DCURL_DISABLE_CRYPTO_AUTH=ON -DCURL_DISABLE_LDAP=ON
> -DCURL_DISABLE_PROXY=ON -DENABLE_IPV6=OFF -DENABLE_UNIX_SOCKETS=OFF
> -DHTTP_ONLY=ON
> -DOPENSSL_CRYPTO_LIBRARY=$(Pipeline.Workspace)/ssl/lib/libcrypto.so.1.1
> -DOPENSSL_INCLUDE_DIR=$(Pipeline.Workspace)/ssl/include
> -DOPENSSL_SSL_LIBRARY=$(Pipeline.Workspace)/ssl/lib/libssl.so.1.1
> -DZLIB_INCLUDE_DIR=$(Pipeline.Workspace)/zlib/include
> -DZLIB_LIBRARY=$(Pipeline.Workspace)/zlib/lib/libz.so.1 . && cmake
> --build build
>
> I can see the following possible relevant build output lines (not
> contiguous) that may indicate ZLib gets correctly integrated:
>
> Found ZLIB: /home/vsts/work/1/zlib/lib/libz.so.1 (found version "1.2.11")
>
> Enabled features: SSL libz AsynchDNS alt-svc HTTPS-proxy
>
> However, I’ve seen in the following answer:
> https://stackoverflow.com/a/29966893
> <https://stackoverflow.com/a/29966893>. Looking at my generated
> libcurl headers, I can’t find any match for “HAVE_LIBZ” (neither in my
> build output).
>

The proper way to specify OpenSSL and zlib locations is by using
OPENSSL_ROOT_DIR [1] and ZLIB_ROOT variables [2], because we call
cmake's find_package and that's what they use. For example:

-DCMAKE_USE_OPENSSL=ON -DOPENSSL_ROOT_DIR=C:\somewhere -DCURL_ZLIB=ON
-DZLIB_ROOT=C:\somewhere

This assumes you've already installed openssl and zlib to those
locations and they have lib,bin,etc. To set the install location when
configuring zlib via cmake you can use -DCMAKE_INSTALL_PREFIX:PATH=. To
set the install location when configuring openssl via Configure you can
use --prefix= and --openssldir=.

Setting ACCEPT_ENCODING to a specific string is almost never used
correctly. What you should do instead is set it to an empty string ""
and libcurl will only send the encodings it actually supports [3].

printf("%s\n", curl_version()) to make sure your program is actually
using the libcurl you built and not some other one in the path.

[1]: https://github.com/Kitware/CMake/blob/master/Modules/FindOpenSSL.cmake
[2]: https://github.com/Kitware/CMake/blob/master/Modules/FindZLIB.cmake
[3]: https://curl.se/libcurl/c/CURLOPT_ACCEPT_ENCODING.html



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Received on 2021-02-05