flymake reporting errors for good code

Question

I am going to put this question in the Emacs site even though it might be a ccls issue. The problem I see and describe below is within Emacs. Emacs version 30.1 on an M1 macOS 15.5.

I am doing development for a “Cheap Yellow Display” which is a ESP32 with a display and some other support chips. I am using PlatformIO rather than the Arduino IDE. With the current set up, I can build and load code whose source is on my Mac onto the development board and run it from within Emacs.

Some of the packages I have loaded in are platformio-mode, lsp-mode, ccls, and projectile. The platformio-mode creates a .ccls file with clang at the top and a number of -I and -D directives pulled from the development environment and pointing to the include files for an embedded eps32.

Much of the system is working. I have more than one issue but I will stick to only one here.

In a file called 2-TouchTest.cpp are a sequence of calls to Serial.print() such as Serial.print("Pressure = “);. All of the calls are flagged with an error 82 2 error l-d---b no matching member function for call to 'print’. Yet, if I do M-. on Serial it goes to the proper definition and if I do M-. on print it brings up the correct list of prototypes:

81:    size_t print(const __FlashStringHelper *ifsh) { return print(reinterpret_cast<const char *>(ifsh)); }
82:    size_t print(const String &);
83:    size_t print(const char[]);
84:    size_t print(char);
85:    size_t print(unsigned char, int = DEC);
86:    size_t print(int, int = DEC);
87:    size_t print(unsigned int, int = DEC);
88:    size_t print(long, int = DEC);
89:    size_t print(unsigned long, int = DEC);
90:    size_t print(long long, int = DEC);
91:    size_t print(unsigned long long, int = DEC);
92:    size_t print(double, int = 2);
93:    size_t print(const Printable&);
94:    size_t print(struct tm * timeinfo, const char * format = NULL);

Edit on 06/21/2025: In today's project, the error is cannot initialize object parameter of type 'Print' with an expression of type 'HardwareSerial' for the line of code Serial.printf("c = %c\n", c); (using printf instead of print)

Answer 1

This is not an emacs issue but a ccls misconfiguration. The first line of the .ccls file is "compiler driver (usually clang)". In my case, I am developing code for a "Cheap Yellow Display", using PlatformIO Core (CLI). This makes the path to the compiler driver ~/.platformio/packages/toolchain-xtensa-esp32/bin/xtensa-esp32-elf-gcc (since the board has an ESP32 SoC).