v3.0.0 linux compilation error due to: "undefined reference to `clock_gettime'"

[KristofferC]

I am getting the following error when attempting to compile v3.0.0 on a linux machine (GCC 7.1.0):

[21:13:06] CMakeFiles/notcurses-demo.dir/src/demo/demo.c.o: In function `main':
[21:13:06] demo.c:(.text.startup+0x3e3): undefined reference to `clock_gettime'
[21:13:06] demo.c:(.text.startup+0x5a6): undefined reference to `clock_gettime'
[21:13:06] demo.c:(.text.startup+0x704): undefined reference to `clock_gettime'
[21:13:06] CMakeFiles/notcurses-demo.dir/src/demo/animate.c.o: In function `animate_demo':
[21:13:06] animate.c:(.text+0xbbe): undefined reference to `clock_gettime'
[21:13:06] CMakeFiles/notcurses-demo.dir/src/demo/highcon.c.o: In function `highcon_demo':
[21:13:06] highcon.c:(.text+0x3b8): undefined reference to `clock_gettime'
[21:13:06] CMakeFiles/notcurses-demo.dir/src/demo/highcon.c.o:highcon.c:(.text+0x57d): more undefined references to `clock_gettime' follow
[21:13:06] collect2: error: ld returned 1 exit status

Doing something like:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d9b9f0f79..7bb9ad13b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -144,6 +144,7 @@ if(WIN32)
 elseif(NOT APPLE)
   find_library(LIBM m REQUIRED)
   find_library(LIBRT rt REQUIRED)
+  set(LIBRT_LIBRARIES rt)
 endif()
 if(NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
   include_directories(/usr/local/include)
@@ -679,6 +680,7 @@ target_include_directories(ncneofetch
 target_link_libraries(ncneofetch
   PRIVATE
     notcurses
+    "${LIBRT_LIBRARIES}"
 )
 
 # documentation source, processed by pandoc into XHTML and man pages. declare

seems to fix it, but I am not experienced enough to know if that makes sense.

[dankamongmen]

good find, good fix. that's a fairly old GCC, but we ought work with it. what distro is this, just for my edification?

your fix looks pretty much right. would you like to make a PR out of it, so you get the commit credit? if not, i'll commit it myself.

[dankamongmen]

sure enough, " Link with -lrt (only for glibc versions before 2.17)."

[dankamongmen]

we actually needed it a few more places, and the desired syntax was a bit different. i believe i've fixed this in b5ccc9d; please verify and let me know! thanks!

[KristofferC]

Thanks for the quick reply and speedy fix. With b5ccc9d things mostly work but I also needed:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c5ed5c171..af94f8fb4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -599,6 +599,7 @@ target_include_directories(notcurses-info
 target_link_libraries(notcurses-info
   PRIVATE
     notcurses
+    "${LIBRT}"
 )
 
 ############################################################################
@@ -616,6 +617,8 @@ target_include_directories(notcurses-input
 target_link_libraries(notcurses-input
   PRIVATE
     notcurses++
+    "${LIBRT}"
+
 )
 
 ############################################################################
@@ -633,6 +636,7 @@ target_include_directories(nctetris
 target_link_libraries(nctetris
   PRIVATE
     notcurses++
+    "${LIBRT}"
 )
 endif()
 
@@ -678,6 +682,7 @@ target_include_directories(ncneofetch
 target_link_libraries(ncneofetch
   PRIVATE
     notcurses
+    "${LIBRT}"
 )
 
 # documentation source, processed by pandoc into XHTML and man pages. declare

that's a fairly old GCC, but we ought work with it. what distro is this, just for my edification?

For context, this came up on a synthetic Alpine linux system which only purpose is to cross-compile libraries to a large number of architectures for use by the Julia Language package manager to deliver binaries to users. It is using an old glibc is to try get maximum compatibility with a large variety of users system, since a binary compiled on an older glibc will work on a system with a newer one but not vice versa. If you are at all interested the system is described shortly in https://youtu.be/S__x3K31qnE?t=264 and you can see the WIP for building notcurses with it in JuliaPackaging/Yggdrasil#4059 where it is built for:

aarch64-apple-darwin
aarch64-linux-gnu
aarch64-linux-musl
armv6l-linux-gnueabihf
armv6l-linux-musleabihf
armv7l-linux-gnueabihf
armv7l-linux-musleabihf
i686-linux-gnu
i686-linux-musl
i686-w64-mingw32
powerpc64le-linux-gnu
x86_64-apple-darwin
x86_64-linux-gnu
x86_64-linux-musl
x86_64-unknown-freebsd
x86_64-w64-mingw32

Looking at the builders in JuliaPackaging/Yggdrasil#4059, the current status seems to be that it builds on most platforms with the exception of:

Apple M1 (aarch64-apple-darwin):

[09:24:03] Undefined symbols for architecture arm64:
[09:24:03]   "___divdc3", referenced from:
[09:24:03]       _normal_demo in normal.c.o
[09:24:03] ld: symbol(s) not found for architecture arm64
[09:24:03] clang-12: error: linker command failed with exit code 1 (use -v to see invocation)

Windows (this one is funny, libdeflate is found by CMake but then immidiately set to NOTFOUND).

[09:23:57] -- The following REQUIRED packages have been found:
[09:23:57] 
[09:23:57]  * PkgConfig
[09:23:57]  * terminfo
[09:23:57]  * Threads
[09:23:57]  * libunistring
[09:23:57]  * libdeflate
[09:23:57] 
[09:23:57] -- Configuring done
[09:23:57] CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
[09:23:57] Please set them or make sure they are set and tested correctly in the CMake files:
[09:23:57] libdeflate
[09:23:57]     linked by target "notcurses-core" in directory /workspace/srcdir/notcurses-3.0.0

FreeBSD - Couldn't find unigbrk.h from GNU libunistrin�g. Not sure what is going on here.

[dankamongmen]

outstanding, thanks for all the info.

the libdeflate one is surprising -- i use libdeflate in MSYS2 without issues.

[dankamongmen]

i've applied your patch from above, and hopefully this solves all remaining problems. thanks a ton!