claws-mail: configure: error: libetpan 0.57 not found

[ryandesign (Ryan Carsten Schmidt)]

​claws-mail fails to configure on Snow Leopard:

checking whether to use libetpan... yes
checking for libetpan-config... /opt/local/bin/libetpan-config
checking libetpan/libetpan.h usability... yes
checking libetpan/libetpan.h presence... yes
checking for libetpan/libetpan.h... yes
checking whether libetpan-config hints compiles and links fine... no
*** Claws Mail requires libetpan 0.57 or newer. See http://www.etpan.org/ 
*** You can use --disable-libetpan if you don't need IMAP4 and/or NNTP support.
configure: error: libetpan 0.57 not found

libetpan is of course installed; config.log shows the reason why it wasn't detected:

configure:20395: checking whether libetpan-config hints compiles and links fine
configure:20409: /usr/bin/gcc-4.2 -o conftest -pipe -Os -arch x86_64 -Wno-unused-function -Wno-pointer-sign -Wall -no-cpp-precomp -fno-common -I/opt/local/include -I/opt/local/include -L/opt/local/lib -Wl,-headerpad_max_install_names -arch x86_64 -Wl,-export_dynamic conftest.c  -lm -lresolv -L/opt/local/lib -letpan -L/opt/local/lib -Wl,-headerpad_max_install_names -L/opt/local/lib -L/opt/local/lib -L/opt/local/lib -lcurl -lidn2 -lpsl -lssl -lcrypto -lssl -lcrypto -lz -lexpat -lz -lssl -lcrypto -liconv -lsasl2 -lssl -lcrypto >&5
ld: unknown option: -export_dynamic
collect2: ld returned 1 exit status

[pmetzger (Perry E. Metzger)]

This works under current Xcode. I'm not sure what the correct way to fix this so it works across more compilers would be. What's recommended?

[ryandesign (Ryan Carsten Schmidt)]

Replying to pmetzger:

This works under current Xcode.

No doubt! But apparently the version of ld on Snow Leopard is too old to know about -export_dynamic. (I was mistaken earlier when I thought it was due to the old compiler because I saw /usr/bin/gcc-4.2 on the line, but -Wl,-export_dynamic means "pass -export_dynamic to the linker", so it's actually the old linker that's causing the problem.)

Ideally, the configure script should first check whether the linker understands a flag before trying to use it. That's the purpose of configure scripts: to determine the capabilities of the system and not make assumptions. Looking at configure.ac, it's unconditionally using -Wl,-export_dynamic on macOS.