Thanks for the clarification! I thought linker flags should be installed globally for all compilation targets.

Another question:

Why don't we set LIBS in the configure in "checking for curl_multi_init" using LIBCURL_LIBS or LIBCURL_LDFLAGS?
https://github.com/postgres/postgres/blob/master/configure#L12734

Like this:
    LIBS="$(LIBCURL_LDFLAGS) $(LIBCURL_LDLIBS)"

And set LIBS with -lcurl.

As I understand we need to check the properties of libcurl we are compiling with? It may be some local libcurl from /opt/my_libcurl. So LIBCURL_... may contain a flag like -L/opt/my_libcurl Without these LIBCURL... variables we will check a system libcurl, not our local.

I mean why don't we set LIBS


current *configure*

$as_echo_n "checking for curl_multi_init in -lcurl... " >&6; }
....
else
  ac_check_lib_save_LIBS=$LIBS
LIBS="-lcurl  $LIBS"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h.  */

https://github.com/postgres/postgres/blob/master/configure#L12734

For example, I've logged flags after this code sample and they don't contain -L/opt/my_libcurl

    IVK configure:13648: CFLAGS=-Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -pipe -O2     IVK configure:13649: LDFLAGS=-Wl,-z,relro -Wl,-z,now -flto=auto -ffat-lto-objects -L/usr/lib/llvm-10/lib -L/usr/local/lib/zstd     IVK configure:13650: LIBS=-lcurl  -lz -lreadline -lpthread -lrt -ldl -lm
    IVK configure:13651: LDLIBS=

On 25-06-23 18:32, Jacob Champion wrote:
On Fri, Jun 20, 2025 at 3:08 AM Ivan Kush <ivan.k...@tantorlabs.com> wrote:
Hello!

This patch fixes CPPFLAGS, LDFLAGS, LIBS when checking AsyncDNS libcurl
support in configure
Hi Ivan, thanks for the report! Your patch puts new logic directly
after an AC_MSG_ERROR() call, so any effect has to come from the fact
that we're no longer restoring the old compiler and linker flags.
That's not what we want -- Curl needs to be isolated from the rest of
the build.

Let's focus on the error you're seeing:

After compilation during testing some Postgres shared libraries or
binaries that was linked with libcurl showed an error "version
CURL_OPENSSL_3 not found (required by …/libcurl.so.4)"
What's your configure line? You need to make sure that your custom
libcurl is used at configure-time, compile-time, and run-time.

And which binaries are complaining? The only thing that should ever be
linked against libcurl is libpq-oauth-18.so.

Thanks,
--Jacob

--
Best wishes,
Ivan Kush
Tantor Labs LLC



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