Warnings#

Warnings are diagnostic messages that report constructions that are not inherently erroneous but that are risky or suggest there is likely to be a bug in the program. Unless -Werror is specified, they do not prevent compilation of the program.

-Wall#: Turns on all warnings messages. Warnings are not a defined part of the D language, and all constructs for which this may generate a warning message are valid code.

-Walloca#: This option warns on all uses of “alloca” in the source.

-Walloca-larger-than=n#: Warn on unbounded uses of alloca, and on bounded uses of alloca whose bound can be larger than n bytes. -Wno-alloca-larger-than disables -Walloca-larger-than warning and is equivalent to -Walloca-larger-than=SIZE_MAX or larger.

-Wcast-result#: Warn about casts that will produce a null or zero result. Currently this is only done for casting between an imaginary and non-imaginary data type, or casting between a D and C++ class.

-Wno-deprecated#: Do not warn about usage of deprecated features and symbols with deprecated attributes.

-Werror#: Turns all warnings into errors.

-Wspeculative#: List all error messages from speculative compiles, such as __traits(compiles, ...). This option does not report messages as warnings, and these messages therefore never become errors when the -Werror option is also used.

-Wtemplates#: Warn when a template instantiation is encountered. Some coding rules disallow templates, and this may be used to enforce that rule.

-Wunknown-pragmas#: Warn when a pragma() is encountered that is not understood by gdc. This differs from -fignore-unknown-pragmas where a pragma that is part of the D language, but not implemented by the compiler, won’t get reported.

-Wno-varargs#: Do not warn upon questionable usage of the macros used to handle variable arguments like va_start.

-fignore-unknown-pragmas#: Turns off errors for unsupported pragmas.

-fmax-errors=n#: Limits the maximum number of error messages to n, at which point gdc bails out rather than attempting to continue processing the source code. If n is 0 (the default), there is no limit on the number of error messages produced.

-fsyntax-only#: Check the code for syntax errors, but do not actually compile it. This can be used in conjunction with -fdoc or -H to generate files for each module present on the command-line, but no other output file.

-ftransition=id#

Report additional information about D language changes identified by id. The following values are supported:

all: List information on all D language transitions.
complex: List all usages of complex or imaginary types.
field: List all non-mutable fields which occupy an object instance.
in: List all usages of in on parameter.
nogc: List all hidden GC allocations.
templates: List statistics on template instantiations.
tls: List all variables going into thread local storage.
vmarkdown: List instances of Markdown replacements in Ddoc.