Various Compiler Warnings in ESP32 Framework after enabling warning flags

[cziter15]

Board

Custom ESP32 board

Device Description

n/a

Hardware Configuration

n/a

Version

latest stable Release (if not listed below)

Type

Task

IDE Name

VSCode

Operating System

n/a

Flash frequency

n/a

PSRAM enabled

yes

Upload speed

n/a

Description

I've enabled extra compiler warnings in the my ksIotFrameworkLib project. After enabling these, a number of warnings appeared when building arduino-esp32. Enabling these flags can help catch potential bugs and improve code quality.

-Wunused-variable            # Warn about unused local variables
-Wunused-parameter           # Warn about unused function parameters
-Wunused-function            # Warn about unused static functions
-Wunused-but-set-variable    # Warn about variables set but never read
-Wsign-compare               # Warn about signed/unsigned comparisons
-Wtype-limits                # Warn about type limit comparisons
-Wmissing-field-initializers # Warn about missing field initializers
-Wuninitialized              # Warn about uninitialized variables
-Wmaybe-uninitialized        # Warn about potentially uninitialized variables
-Wformat                     # Warn about printf/scanf format issues
-Wreturn-type                # Warn about missing return statements
-Wswitch                     # Warn about missing switch cases
-Wparentheses                # Warn about ambiguous parentheses
-Wsequence-point             # Warn about undefined behavior
-Wstrict-aliasing            # Warn about strict aliasing violations
-Wextra                      # Enable additional warnings beyond -Wall

I don’t necessarily recommend enabling these flags directly in the Arduino-ESP32 framework, but they can at least help resolve the issues listed. There may be more similar cases, so some form of automation could be very helpful.

For example, an unused parameter warning can be suppressed in several ways:

void myFunction(int x)
{
    (void)x; // Silence unused parameter warning
}

or

void myFunction(int /*x*/)
{
    // x is unused
}

or in C++17 and later:

void myFunction([[maybe_unused]] int x)
{
    // x is unused
}

Warnings in Build

Network

• NetworkClient.cpp:510 – comparison of integer expressions of different signedness (long unsigned int vs int)
• NetworkInterface.cpp:49 – unused parameter arg

Ethernet

• ETH.cpp:55 – unused parameter arg
• ETH.cpp:98 – unused parameter event_data
• ETH.cpp:445 – unused parameter ctx
• ETH.cpp:919 – unused parameter bus_pointer

WiFi

• WiFiGeneric.cpp:70 – unused parameter arg

NetworkClientSecure / SSL

• ssl_client.cpp:29 – unused parameters function, line
• ssl_client.cpp:228 – comparison of integer expressions of different signedness (int vs size_t)

Update

• Updater.cpp:130 – unused parameter label
• Updater.cpp:283 – comparison of integer expressions of different signedness (int vs unsigned int)

ESPmDNS

• ESPmDNS.cpp:287 – comparison of integer expressions of different signedness (int vs size_t)
• ESPmDNS.cpp:368 – comparison of integer expressions of different signedness (int vs size_t)
• ESPmDNS.cpp:384 – comparison of integer expressions of different signedness (int vs size_t)

Hash

• PBKDF2_HMACBuilder.cpp:112 – unused parameters stream, maxLen

AsyncUDP

• AsyncUDP.cpp:166 – unused parameter pvParameters
• AsyncUDP.cpp:347 – unused parameter rport
• AsyncUDP.cpp:773 – unused parameter upcb

DNSServer

• DNSServer.cpp:136 – comparison of integer expressions of different signedness (int vs size_t)

LittleFS

• LittleFS.cpp:46 – unused parameter maxOpenFiles

WebServer / Middleware

• Middleware.h:17 – unused parameter server (multiple files: Middleware, AuthenticationMiddleware, CorsMiddleware, LoggingMiddleware, MiddlewareChain)
• Parsing.cpp:192 – comparison of integer expressions of different signedness (size_t vs int)
• Parsing.cpp:209 – comparison of integer expressions of different signedness (size_t vs int)
• Parsing.cpp:379 – comparison of integer expressions of different signedness (long unsigned int vs const long int)
• Parsing.cpp:398 – comparison of integer expressions of different signedness (long unsigned int vs const long int)
• RequestHandlersImpl.h:73 – unused parameter requestUri
• RequestHandlersImpl.h:97 – unused parameter requestUri
• WebServer.cpp:145 – unused parameters mode, params
• WebServer.cpp:616 – NetworkClient::flush() is deprecated; use clear() instead

Sketch

n/a

Debug Message

n/a

Other Steps to Reproduce

No response

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[lbernstone]

This is largely a function of the IDE. In Arduino IDE, you have a dropdown for the level of compiler warnings (none, default, more, all). More = -Wall, all = -Wall -Wextra. I think more would include everything you posted. I definitely would recommend people use all, but that is very likely to log a lot of issues on older libraries.

[SuGlider]

@cziter15 - Thanks for the issue report.

Those warnings are not "dangerous" in the sense that they may cause a misinterpretation from different compilers that may end in different execution behaviours.

But I agree that improving code quality is the safer way to go. I'll take a look.

[cziter15]

@SuGlider sure thing, it has no functional impact. Just good idea to silence them. Great job for Copilot agent btw.