Resources:

GCC Flags

Summary:


# Options I use
-Wall -Wextra -Werror -pedantic -std=c17 -Wformat=2 -Wformat-truncation -Wundef -Wfloat-conversion -Wdouble-promotion -Wshadow -Wcast-align -Wsign-conversion

# Warnings I disable
-Wno-unused-variable -Wno-unused-function -Wno-unused-parameter -Wno-missing-field-initializers -Wno-missing-braces

# Debug flags
-O0 -g -DDEBUG

# Optimized flags
-O3 -march=native

# Other
-Icode/    # Add "code/" to include directories
-lm        # Link library "m"
-o blah    # Sets output file to "blah"

# Also: When using interfacing with Linux,
# you might need to define _POSIX_C_SOURCE
# or _GNU_SOURCE

Options I use:

-Wall: Enable a lot of warnings (but contrary to the name, not all)
-Wextra: Enable even more warnings
-Werror: Make the compilation fail if any warnings are generated
-pedantic: Create a warning if the code is not following the C standard (e.g. using gnu-extensions)
-std=c17: Specify the standard to follow (here: C17)
-Wformat=2: For e.g. printf / scanf, check the format strings against the provided function parameters and warn on mismatch
- When defining a custom variadic function which takes e.g. printf-style arguments, you can enable warnings by adding e.g. __attribute__((format(printf, 1, 2))) in front of the function definition
- Format: format(archetype, string-index, first-to-check)
-Wformat-truncation: For e.g. snprintf, warn if the output might be truncated
-Wundef: Warn if an undefined identifier is evaluated in an #if directive
-Wfloat-conversion: Warn about implicit conversions which reduce the precision of a real value (e.g. double -> float or float -> int)
-Wdouble-promotion: Warn about implicit conversion from float to double
-Wshadow: Warn if a variable or type shadows another.
-Wcast-align: Warn if casting a pointer requires a stricter alignment.
-Wsign-conversion: Warn about implicit conversions which change the sign of an integer value

Warnings I disable:

-Wno-unused-variable: Don't warn on unused variables
-Wno-unused-function: Don't warn on unused functions
-Wno-unused-parameter: Don't warn on unused function parameters
-Wno-missing-field-initializers: When initializing a struct, don't warn if an initializer of some field is missing (C standard mandates that a field without an initializer is implicitly set to 0)
-Wno-missing-braces: For nested struct / unions, don't warn if an initializer is not fully bracketed

Debug flags:

-O0: Disable optimizations
-g: Produce debugging information
-DDEBUG: Predefines the macro DEBUG to 1 (preprocessor can then check for debug/release builds using #ifdef DEBUG [...] #else [...] #endif)

Release flags:

-O3: Enable (most) optimizations
-march=native: Enable usage of instructions which are supported by the local machine