Compiler warnings with apple-clang 17

[jb-gcx]

In my environment (Apple clang version 17.0.0) I get the following warnings:

[build] plotlypp/plotly_min_js.hpp:16:1: warning: string literal of length 4653932 exceeds maximum length 65536 that C++ compilers are required to support [-Woverlength-strings]
[build]    16 | R"d0(/**
[build]       | ^~~~~~~~
[build]    17 | * plotly.js v3.0.1
[build]       | ~~~~~~~~~~~~~~~~~~
[build]    18 | * Copyright 2012-2025, Plotly, Inc.
[build]       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    19 | * All rights reserved.
[build]       | ~~~~~~~~~~~~~~~~~~~~~~
[build]    20 | * Licensed under the MIT license
[build]       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    21 | */
[build]       | ~~
[build]    22 | (
[build]       | ~
[build]    23 |  function(root, factory) {
[build]       |  ~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    24 |   if (typeof module === "object" && module.exports) {
[build]       |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    25 |    module.exports = factory();
[build]       |    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    26 |   } else {
[build]       |   ~~~~~~~~
[build]    27 |    root.moduleName = factory();
[build]       |    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    28 |   }
[build]       |   ~
[build]    29 | } (typeof self !== "undefined" ? self : this, () => {
[build]       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build]    30 | "use strict";var Plotly=(()=>{var VQe=Object.create;var MS=Object.defineProperty,HQe=Object.defineProperties,GQe=Object.getOwnPropertyDescriptor,jQe=Object.getOwnPropertyDescriptors,WQe=Object.getOwnPropertyNames,XQ=Object.getOwnPropertySymbols,ZQe=Object.getPrototypeOf,KQ=Object.prototype.hasOwnProperty,XQe=Object.prototype.propertyIsEnumerable;var YQ=(e,t,r)=>t in e?MS(e,t,{enumerable:!0,configurable:!0,writable:!0,value:r}):e[t]=r,JQ=(e,t)=>{for(var r in t||(t={}))KQ.call(t,r)&&YQ(e,r,t[r]);if(XQ)for(var r of XQ(t))XQe.call(t,r)&&YQ(e,r,t[r]);return e},$Q=(e,t)=>HQe(e,jQe(t));var Ll=(e,t)=>()=>(e&&(t=e(e=0)),t);var ye=(e,t)=>()=>(t||e((t={exports:{}}).exports,t),t.exports),QQ=(e,t)=>{for(var r in t)MS(e,r,{get:t[r],enumerable:!0})},eee=(e,t,r,n)=>{if(t&&typeof t=="object"||typeof t=="function")for(let i of WQe(t))!KQ.call(e,i)&&i!==r&&MS(e,i,{get:()=>t[i],enumerable:!(n=GQe(t,i))||n.enumerable});return e};var YQe=(e,t,r)=>(r=e!=null?VQe(ZQe(e)):{},eee(t||!e||!e.__esModule?MS(r,"default",{value:e,enumerable:!0}):r,e)),B1=e=>eee(MS({},"__esModule",{value:!0}),e);var e6=ye(tee=>{"use strict";tee.version="3.0.1"});var iee=ye((ree,t6)=>{(function(t,r,n){r[t]=r[t]||n(),typeof t6!="undefined"&&t6.exports&&(t6.exports=r[t])})("Promise",typeof window!="undefined"?window:ree,function(){"use strict";var t,r,n,i=Object.prototype.toString,a=typeof setImmediate!="undefined"?function(E){return setImmediate(E)}:setTimeout;try{Object.defineProperty({},"x",{}),t=function(E,k,A,L){return Object.defineProperty(E,k,{value:A,writable:!0,configurable:L!==!1})}}catch(p){t=function(k,A,L){return k[A]=L,k}}n=function(){var E,k,A;function L(_,C){this.fn=_,this.self=C,this.next=void 0}return{add:function(C,M){A=new L(C,M),k?k.next=A:E=A,k=A,A=void 0},drain:function(){var C=E;for(E=k=r=void 0;C;)C.fn.call(C.self),C=C.next}}}();function o(p,E){n.add(p,E),r||(r=a(n.drain))}function s(p){var E,k=typeof p;return p!=null&&(k=="object"||k=="function")&&(E=p.then),typeof E=="function"?E:!1}function l(){for(var p=0;p<this.chain.length;p++)u(this,this.state===1?this.chain[p].success:this.chain[p].failure,this.chain[p]);this.chain.length=0}function u(p,E,k){var A,L;try{E===!1?k.reject(p.msg):(E===!0?A=p.msg:A=E.call(void 0,p.msg),A===k.promise?k.reject(TypeError("Promise-chain cycle")):(L=s(A))?L.call(A,k.resolve,k.reject):k.resolve(A))}catch(_){k.reject(_)}}function c(p){var E,k=this;if(!k.triggered){k.triggered=!0,k.def&&(k=k.def);try{(E=s(p))?o(function(){var A=new d(k);try{E.call(p,function(){c.apply(A,arguments)},function(){f.apply(A,arguments)})}catch(L){f.call(A,L)}}):(k.msg=p,k.state=1,k.chain.length>0&&o(l,k))}catch(A){f.call(new d(k),A)}}}function f(p){var E=this;E.triggered||(E.triggered=!0,E.def&&(E=E.def),E.msg=p,E.state=2,E.chain.length>0&&o(l,E))}function h(p,E,k,A){for(var L=0;L<E.length;L++)(function(C){p.resolve(E[C]).then(function(g){k(C,g)},A)})(L)}function d(p){this.def=p,this.triggered=!1}function v(p){this.promise=p,this.state=0,this.triggered=!1,this.chain=[],this.msg=void 0}function x(p){if(typeof p!="function")throw TypeError("Not a function");if(this.__NPO__!==0)throw TypeError("Not a promise");this.__NPO__=1;var E=new v(this);this.then=function(A,L){var _={success:typeof A=="function"?A:!0,failure:typeof L=="function"?L:!1};return _.promise=new this.constructor(function(M,g){if(typeof M!="function"||typeof g!="function")throw TypeError("Not a function");_.resolve=M,_.reject=g}),E.chain.push(_),E.state!==0&&o(l,E),_.promise},this.catch=function(A){return this.then(void 0,A)};try{p.call(void 0,function(A){c.call(E,A)},function(A){f.call(E,A)})}catch(k){f.call(E,k)}}var b=t({},"constructor",x,!1);return x.prototype=b,t(b,"__NPO__",0,!1),t(x,"resolve",function(E){var k=this;return E&&typeof E=="object"&&E.)d0"
[build]       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And

[build] plotlypp/figure.hpp:54:37: warning: lambda capture 'this' is not used [-Wunused-lambda-capture]
[build]    54 |         auto html_safe_serialize = [this](const auto& json) {
[build]       |                                     ^~~~
[build] 2 warnings generated.

The second warning seems like an easy fix. The first one might be more difficult, maybe #embed is a solution where available?

Making warnings ignorable

nlohmann_json has an easy way for consumers to ignore warnings in its headers by providing the option: option(JSON_SystemInclude "Include as system headers (skip for clang-tidy)." OFF). When set, this option configures the include directories as SYSTEM directories, which suppresses warnings from them.

I would greatly appreciate a similar option for plotlypp, so I can choose to ignore warnings in plotlypp headers.

Right now I'm using this workaround to ignore the warnings:

get_target_property(plotlypp_interface_include_dirs plotlypp::plotlypp INTERFACE_INCLUDE_DIRECTORIES)
target_include_directories(my_executable SYSTEM PRIVATE ${plotlypp_interface_include_dirs})
target_link_libraries(my_executable PRIVATE nlohmann_json::nlohmann_json) # has to be linked manually, because we lose transitive dependencies from plotlypp

[jimmyorourke]

The second is an easy fix, and a good reminder to turn on warnings for the test/example targets. I hesitate to do so on the library targets since it's an interface target.

The first warning is interesting. I had researched this and was under the impression that it was actually MSVC that had the string literal limitations, and my understanding was that prior to Visual Studio 2022 version 17 the limit was 65535 bytes, but after that version the limit was 65535 for each quoted literal, but unlimited up to available memory after concatenation. This was the reason for the chunking of quoted and concatenated literals.
#embed requires C++26 unfortunately. So it is interesting the warning appears on apple clang.
I'll look into this a little more, but likely just suppress the warning. The CI builds across platforms and compilers giving me some confidence this isn't a critical issue.

[jimmyorourke]

Ah I see, the string length warning occurs with -Wpedantic, but only on Clang. I had considered a byte array but was concerned about the bloat from the increase in both file size and compile time. For now we'll and an option to suppress the warnings.

In #10 I've added a bunch of warnings on the example target to detect any issues in the library itself, suppressing only -Woverlength-strings on clang for now.
I've also added the PLOTLYPP_SYSTEM_INCLUDE cmake option. Thanks for the idea.

Another note regarding your current workaround, I think it can actually be simplified (even though now it should be unnecessary).
I think this should work

# link as normal -- nlohmann json sub-dependency will get linked as expected
target_link_libraries(my_executable  PRIVATE plotlypp::plotlypp)
# override the include directories to be treated as system
target_include_directories(my_executable SYSTEM PRIVATE
    $<TARGET_PROPERTY:plotlypp::plotlypp,INTERFACE_INCLUDE_DIRECTORIES>
)

Thanks for continuing to help improve this project!

[jb-gcx]

Thanks again for the very quick help. Loving the library so far 💪

#embed requires C++26 unfortunately. So it is interesting the warning appears on apple clang.
I'll look into this a little more, but likely just suppress the warning. The CI builds across platforms and compilers giving me some confidence this isn't a critical issue.

You could gate #embed behind a feature check for __cpp_pp_embed. That only solves the problem for modern compilers of course, but it's a start.

That being said, I agree that it's not particularly important to fix. I'd expect a reasonable compiler to error if it actually can't handle the literal. Suppressing seems fine.

# link as normal -- nlohmann json sub-dependency will get linked as expected
target_link_libraries(my_executable  PRIVATE plotlypp::plotlypp)
# override the include directories to be treated as system
target_include_directories(my_executable SYSTEM PRIVATE
    $<TARGET_PROPERTY:plotlypp::plotlypp,INTERFACE_INCLUDE_DIRECTORIES>
)

I considered this too, but as far as I know the behavior becomes compiler dependent. When an include dir gets passed as both a regular and a system include, the behavior might depend on the order they're passed in. Don't get me wrong, this approach probably works for all major compilers, but I'd like to avoid relying on it if possible.

As you say, it's obsolete anyway due to the new option you kindly provided 👍

Edit: One more thought, it might be better to suppress -Woverlength-strings locally in the affected header using diagnostic #pragmas. That way users that include the library in a project with -Wpedantic aren't forced to set the PLOTLYPP_SYSTEM_INCLUDE option to get rid of the warning. It's not relevant for my use-case but might be a good improvement for others.

[jimmyorourke]

Ah yes, I meant to do that but got too focused on the system includes idea.

#11 adds the explicit warning suppression within the the plotlypp header. With this you should not need to treat it as a system library.