Release build fails when JSON diagnostics enabled

[IvanPizhenko]

Description

Release build fails when -DJSON_DIAGNOSTICS=1 -DJSON_DIAGNOSTIC_POSITIONS=1 are in effect.

Reproduction steps

Please see attached ZIP archive json_release_build_failure.zip with minimal reproducible example.
I'm using Ubuntu 24.04 LTS and GCC 13 (standard GCC version on that Ubuntu).

OS preparation:
Install C++ compiler and cmake, if you don't have them already:

sudo apt install -y build-essential cmake

Sample project is "standard" CMake based project.

1. Unpack attached archive in the empty directory.
2. Run commands to build in Release mode:

mkdir build-release
cd build-release
cmake -DCMAKE_BUILD_TYPE=Release ..
make

This should fail.

Now edit CMakeLists.txt, comment out line where symbols -DJSON_DIAGNOSTICS=1 -DJSON_DIAGNOSTIC_POSITIONS=1 are added to the CMAKE_CXX_FLAGS.

Remove directory build-release and try steps above once again. Now it compiles and runs.

IMO diagnostics options must work in Release builds too.

Expected vs. actual results

Debug build compiles and runs as expected, no matter diagnostic options are in effect or not.
Release build fails to compile if diagnostic options are in effect.

Minimal code example

In attached ZIP archive.
json_release_build_failure.zip

Error messages

Too long to paste here. See attached file build.log.

Compiler and operating system

Ubuntu 24.04 LTS, GCC 13

Library version

633de8e

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.

[IvanPizhenko]

json_release_build_failure.zip

[IvanPizhenko]

build.log

[nlohmann]

Hi @IvanPizhenko, thanks for reporting! Can you please try the fix in #5744?

[IvanPizhenko]

Hi @IvanPizhenko, thanks for reporting! Can you please try the fix in #5744?

Hi @nlohmann , confirmed - it works for me.