[Buildroot] [PATCH v2 1/1] package/cpp-httplib: link with libatomic if needed

[Buildroot] [PATCH v2 1/1] package/cpp-httplib: link with libatomic if needed

[Bernd Kuhls]

Buildroot commit 8dad17ea06260ef0bd23eebc47c95a8510310bf5 bumped the
package from 0.27.0 to 0.37.2. This bump includes upstream commit
https://github.com/yhirose/cpp-httplib/commit/464867a9cedef2b6185e25e3e912d3f796fe58fd
which added WebSocket support to version 0.33.0 and causes a build error
detected by the Gitlab pipelines for bootlin-sparc-uclibc:

/builds/bkuhls/buildroot/br-test-pkg/bootlin-sparc-uclibc/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/14.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld:
 /tmp/cciyXsAR.ltrans6.ltrans.o: in function
 `httplib::ws::WebSocket::close(httplib::ws::CloseStatus,
 std::__cxx11::basic_string<char, std::char_traits<char>,
 std::allocator<char> > const&)':
<artificial>:(.text+0x6408): undefined reference to `__atomic_exchange_1'

To fix the problem we add -latomic to LDFLAGS when needed.

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
---
v2: Added -latomic to LDFLAGS (Thomas)

Gitlab pipelines passed:
https://gitlab.com/bkuhls/buildroot/-/commits/2364b86e92f24042ca7f9494b427321527b26adb

 package/cpp-httplib/Config.in      | 2 ++
 package/cpp-httplib/cpp-httplib.mk | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/package/cpp-httplib/Config.in b/package/cpp-httplib/Config.in
index 9bd93ee0af..83251e8eeb 100644
--- a/package/cpp-httplib/Config.in
+++ b/package/cpp-httplib/Config.in
@@ -1,9 +1,11 @@
 comment "cpp-httplib needs a toolchain w/ C++, wchar, threads"
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || !BR2_TOOLCHAIN_HAS_THREADS
 
 config BR2_PACKAGE_CPP_HTTPLIB
 	bool "cpp-httplib"
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_USE_WCHAR
 	help
diff --git a/package/cpp-httplib/cpp-httplib.mk b/package/cpp-httplib/cpp-httplib.mk
index 94f270df94..c9649936e4 100644
--- a/package/cpp-httplib/cpp-httplib.mk
+++ b/package/cpp-httplib/cpp-httplib.mk
@@ -13,6 +13,12 @@ CPP_HTTPLIB_INSTALL_STAGING = YES
 CPP_HTTPLIB_CONF_OPTS = \
 	-Dtest=false
 
+CPP_HTTPLIB_LDFLAGS = $(TARGET_LDFLAGS)
+
+ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
+CPP_HTTPLIB_LDFLAGS += -latomic
+endif
+
 ifeq ($(BR2_PACKAGE_CPP_HTTPLIB_COMPILE),y)
 CPP_HTTPLIB_CONF_OPTS += -Dcompile=true
 CPP_HTTPLIB_DEPENDENCIES += host-python3
-- 
2.47.3

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Re: [Buildroot] [PATCH v2 1/1] package/cpp-httplib: link with libatomic if needed

[Thomas Petazzoni via buildroot]

On Sun, Sep 20, 2026 at 07:50:43PM +0200, Bernd Kuhls wrote:
> Buildroot commit 8dad17ea06260ef0bd23eebc47c95a8510310bf5 bumped the
> package from 0.27.0 to 0.37.2. This bump includes upstream commit
> https://github.com/yhirose/cpp-httplib/commit/464867a9cedef2b6185e25e3e912d3f796fe58fd
> which added WebSocket support to version 0.33.0 and causes a build error
> detected by the Gitlab pipelines for bootlin-sparc-uclibc:
> 
> /builds/bkuhls/buildroot/br-test-pkg/bootlin-sparc-uclibc/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/14.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld:
>  /tmp/cciyXsAR.ltrans6.ltrans.o: in function
>  `httplib::ws::WebSocket::close(httplib::ws::CloseStatus,
>  std::__cxx11::basic_string<char, std::char_traits<char>,
>  std::allocator<char> > const&)':
> <artificial>:(.text+0x6408): undefined reference to `__atomic_exchange_1'
> 
> To fix the problem we add -latomic to LDFLAGS when needed.
> 
> Signed-off-by: Bernd Kuhls <bernd@kuhls.net>

Applied to master, thanks!

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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