nasm/asm/warnings.dat

all [group] all possible warnings
    \c{all} is an group alias for \e{all} warning classes.  Thus, \c{-w+all}
    enables all available warnings, and \c{-w-all} disables warnings
    entirely (since NASM 2.13).

db-empty [on] no operand for data declaration
    Warns about a \c{D}\e{x} declaration
    with no operands, producing no output.
    This is permitted, but often indicative of an error.
    See \k{db}.

ea-absolute [on] absolute address cannot be RIP-relative
    Warns that an address that is inherently absolute cannot
    be generated with RIP-relative encoding using \c{REL},
    see \k{default-rel}.

ea-dispsize [on] displacement size ignored on absolute address
    Warns that NASM does not support generating displacements for
    inherently absolute addresses that do not match the address size
    of the instruction.

float-denorm [off] floating point denormal
    Warns about denormal floating point constants.

float-overflow [on] floating point overflow
    Warns about floating point underflow.

float-toolong [on] too many digits in floating-point number
    Warns about too many digits in floating-point numbers.

float-underflow [off] floating point underflow
    Warns about floating point underflow (a nonzero
    constant rounded to zero.)

forward [on] forward reference may have unpredictable results
    Warns that a forward reference is used which may have
    unpredictable results, notably in a \c{RESB}-type
    pseudo-instruction. These would be \i\e{critical
    expressions} (see \k{crit}) but are permitted in a
    handful of cases for compatibility with older
    versions of NASM. This warning should be treated as a
    severe programming error as the code could break at
    any time for any number of reasons.

implicit-abs-deprecated [on] implicit DEFAULT ABS is deprecated
    Warns that in a future version of NASM, the 64-bit default
    addressing form is likely to change from \c{DEFAULT ABS} to
    \c{DEFAULT REL}. If absolute addressing is indeed intended, it is
    strongly recommended to specify \c{DEFAULT ABS} explicitly.

label-orphan [on] labels alone on lines without trailing \c{:}
=orphan-labels
    Warns about source lines which contain no instruction but define
    a label without a trailing colon. This is most likely indicative
    of a typo, but is technically correct NASM syntax (see \k{syntax}.)

label-redef [off] label redefined to an identical value
    Warns if a label is defined more than once, but the
    value is identical. It is an unconditional error to
    define the same label more than once to \e{different} values.

#
# label-redef-late defaults to an error, as this should never
# actually happen.  Just in case this is a backwards
# compatibility problem, still make it a warning so that the
# user can suppress or demote it.
#
label-redef-late [err] label (re)defined during code generation
    The value of a label changed during the final, code-generation
    pass. This may be the result of strange use of the
    preprocessor. This is very likely to produce incorrect code and
    may end up being an unconditional error in a future
    version of NASM.

number-deprecated-hex [on] $ prefix for hexadecimal is deprecated
    Warns that the \c{$} prefix for hexadecimal numbers is
    deprecated, due to the syntactic conflict with \c{$} used
    as a symbol escape prefix. This syntax may be disabled by
    default in a future version of NASM. Replace \c{$} with \c{0x}
    to ensure compatibility with future versions.

number-overflow [on] numeric constant does not fit
    Covers warnings about numeric constants which
    don't fit in 64 bits.

obsolete-nop [on] instruction obsolete and is a noop on the target CPU
    Warns for an instruction which has been removed
    from the architecture, but has been architecturally
    defined to be a noop for future CPUs.

obsolete-removed [on] instruction obsolete and removed on the target CPU
    Warns for an instruction which has been removed
    from the architecture, and is no longer included
    in the CPU definition given in the \c{[CPU]}
    directive, for example \c{POP CS}, the opcode for
    which, \c{0Fh}, instead is an opcode prefix on
    CPUs newer than the first generation 8086.

obsolete-valid [on] instruction obsolete but valid on the target CPU
    Warns for an instruction which has been removed
    from the architecture, but is still valid on the
    specific CPU given in the \c{CPU} directive. Code
    using these instructions is most likely not
    forward compatible.

other [on] any warning not assigned to a specific warning class
    Specifies any warning not included in any specific warning class.

phase [off] phase error during stabilization
    Warns about symbols having changed values during
    the second-to-last assembly pass. This is not
    inherently fatal, but may be a source of bugs.

pp-else-elif [on] \c{%elif} after \c{%else}
    Warns that an \c{%elif}-type directive was encountered
    after \c{%else} has already been encounted. As a result, the
    content of the \c{%elif} will never be expanded.

pp-else-else [on] \c{%else} after \c{%else}
    Warns that a second \c{%else} clause was found for
    the same \c{%if} statement. The content of this \c{%else}
    clause will never be expanded.

pp-empty-braces [on] empty \c{%\{\}} construct
    Warns that an empty \c{%\{\}} was encountered.
    This expands to a single \c{%} character, which
    is normally the \c{%} arithmetic operator.

pp-environment [on] nonexistent environment variable
=environment
    Warns if a nonexistent environment variable
    is accessed using the \c{%!} preprocessor
    construct (see \k{getenv}.)  Such environment
    variables are treated as empty (with this
    warning issued) starting in NASM 2.15;
    earlier versions of NASM would treat this as
    an error.

pp-macro-def-case-single [on] single-line macro defined both case sensitive and insensitive
=macro-def-case-single
    Warns when a single-line macro is defined both case
    sensitive and case insensitive.
    The new macro
    definition will override (shadow) the original one,
    although the original macro is not deleted, and will
    be re-exposed if the new macro is deleted with
    \c{%undef}, or, if the original macro is the case
    insensitive one, the macro call is done with a
    different case.

pp-macro-def-greedy-single [on] single-line macro
=macro-def-greedy-single
    Warns that a single-line macro is defined which would match a
    previously existing greedy definition.  The new macro definition
    will override (shadow) the original one, although the original
    macro is not deleted, and will be re-exposed if the new macro is
    deleted with \c{%undef}, and will be invoked if called with a
    parameter count that does not match the new definition.

# The immediately previous versions of NASM considered
# this an error, so promote this warning is promoted to
# to error by default.
pp-macro-def-param-single [err] single-line macro defined with and without parameters
=macro-def-param-single
    Warns if the same single-line macro is defined with and without
    parameters.  The new macro definition will override (shadow) the
    original one, although the original macro is not deleted, and will
    be re-exposed if the new macro is deleted with \c{%undef}.

pp-macro-defaults [on] macros with more default than optional parameters
=macro-defaults
    Warns when a macro has more default parameters than optional parameters.
    See \k{mlmacdef} for why one might want to disable this warning.

pp-macro-params-legacy [on] improperly calling multi-line macro for legacy support
=macro-params-legacy
    Warns about \i{multi-line macros} being invoked
    with the wrong number of parameters, but for bug-compatibility
    with NASM versions older than 2.15, NASM tried to fix up the
    parameters to match the legacy behavior and call the macro anyway.
    This can happen in certain cases where there are empty arguments
    without braces, sometimes as a result of macro expansion.

    The legacy behavior is quite strange and highly context-dependent,
    and can be disabled with:

    \c      %pragma preproc sane_empty_expansion true

    It is highly recommended to use this option in new code.

pp-macro-params-multi [on] multi-line macro calls with wrong parameter count
=macro-params-multi
    Warns about \i{multi-line macros} being invoked
    with the wrong number of parameters. See \k{mlmacover} for an
    example of why you might want to disable this warning.

pp-macro-params-single [on] single-line macro calls with wrong parameter count
=macro-params-single
    Warns about \i{single-line macros} being invoked
    with the wrong number of parameters.

pp-macro-redef-multi [on] redefining multi-line macro
    Warns that a multi-line macro is being redefined,
    without first removing the old definition with
    \c{%unmacro}.

pp-open-braces [on] unterminated \c{%\{...\}}
    Warns that a preprocessor parameter
    enclosed in braces \c{%\{...\}} lacks the
    terminating \c{\}} character.

pp-open-brackets [on] unterminated \c{%[...]}
    Warns that a preprocessor \c{%[...]} construct
    lacks the terminating \c{]} character.

pp-open-string [on] unterminated string
    Warns that a quoted string without a closing quotation
    mark was encountered during preprocessing.

pp-rep-negative [on] regative \c{%rep} count
=negative-rep
    Warns about a negative count given to the \c{%rep}
    preprocessor directive.

pp-sel-range [on] \c{%sel()} argument out of range
    Warns that the \c{%sel()} preprocessor function was passed
    a value less than 1 or larger than the number of available
    arguments.

pp-trailing [on] trailing garbage ignored
    Warns that the preprocessor encountered additional text
    where no such text was expected. This can
    sometimes be the result of an incorrectly written expression,
    or arguments that are inadvertently separated.

pragma-bad [off] malformed \c{%pragma}
=bad-pragma
    Warns about a malformed or otherwise unparsable
    \c{%pragma} directive.

pragma-empty [off] empty \c{%pragma} directive
    Warns about a \c{%pragma} directive containing nothing.
    This is treated identically to \c{%pragma ignore} except
    for this optional warning.

# Not implemented yet
pragma-na [off] \c{%pragma} not applicable to this compilation
=not-my-pragma
    Warns about a \c{%pragma} directive which is not applicable to
    this particular assembly session.  This is not yet implemented.

pragma-unknown [off] unknown \c{%pragma} facility or directive
=unknown-pragma
    Warns about an unknown \c{%pragma} directive.
    This is not yet implemented for most cases.

prefix-bnd [on] invalid \c{BND} prefix
=bnd
    Warns about ineffective use of the \c{BND} prefix when the
    \c{JMP} instruction is converted to the \c{SHORT} form.
    This should be extremely rare since the short \c{JMP} only
    is applicable to jumps inside the same module, but if
    it is legitimate, it may be necessary to use
    \c{bnd jmp dword}.

prefix-hint-dropped [on] invalid branch hint prefix dropped
    Warns that the \c{{PT}} (predict taken) or \c{{PN}}
    (predict not taken) branch prediction hint prefixes
    are specified on an instruction that does not take
    these prefixes. As these prefixes alias the segment
    override prefixes, this may be a very serious error,
    and therefore NASM will not generate these prefixes.
    To force these prefixes to be emitted, use \c{DS} or
    \c{CS}, instead, respectively.

prefix-hle [on] invalid HLE prefix
=hle
    Warns about invalid use of the HLE \c{XACQUIRE} or \c{XRELEASE}
    prefixes.

prefix-invalid [on] invalid prefix for instruction
    Warns about an instruction which is only valid with certain
    combinations of prefixes. The prefix will still be generated as
    requested, but the result may be a completely different
    instruction or result in a \c{#UD} trap.

prefix-lock-error [on] \c{LOCK} prefix on unlockable instruction
=lock
    Warns about \c{LOCK} prefixes specified on unlockable instructions.

prefix-lock-xchg [on] superfluous \c{LOCK} prefix on \c{XCHG} instruction
    Warns about a \c{LOCK} prefix added to an \c{XCHG} instruction.
    The \c{XCHG} instruction is \e{always} locking, and so this
    prefix is not necessary; however, NASM will generate it if
    explicitly provided by the user, so this warning indicates that
    suboptimal code is being generated.

prefix-opsize [on] invalid operand size prefix
    Warns that an operand prefix (\c{o16}, \c{o32}, \c{o64},
    \c{osp}) invalid for the specified instruction has been specified.
    The operand prefix will be ignored by the assembler.

prefix-seg [on] segment prefix ignored in 64-bit mode
    Warns that an \c{es}, \c{cs}, \c{ss} or \c{ds} segment override
    prefix has no effect in 64-bit mode. The prefix will still be
    generated as requested.

ptr [on] non-NASM keyword used in other assemblers
    Warns about keywords used in other assemblers that
    might indicate a mistake in the source code.
    Currently only the MASM \c{PTR} keyword is
    recognized. If (limited) MASM compatibility is
    desired, the \c{%use masm} macro package is
    available, see \k{pkg_masm}; however, carefully note
    the caveats listed.

regsize [on] register size specification ignored
    Warns about a register with implicit size (such as \c{EAX}, which
    is always 32 bits) been given an explicit size specification which
    is inconsistent with the size of the named register, e.g. \c{WORD
    EAX}. \c{DWORD EAX} or \c{WORD AX} are permitted, and do not
    trigger this warning. Some registers which \e{do not} imply a
    specific size, such as \c{K0}, may need this specification unless
    the instruction itself implies the instruction size:

    \c      KMOVW K0,[foo]          ; OK: KMOVW = 16 bits
    \c      KMOV  WORD K0,[foo]     ; OK: WORD K0 = 16 bits
    \c      KMOV  K0,WORD [foo]     ; OK: WORD [foo] = 16 bits
    \c      KMOV  K0,[foo]          ; Error: unknown size

reloc-abs-byte [off] 8-bit absolute section-crossing relocation
    Warns that an 8-bit absolute relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-abs-dword [off] 32-bit absolute section-crossing relocation
    Warns that a 32-bit absolute relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-abs-qword [off] 64-bit absolute section-crossing relocation
    Warns that a 64-bit absolute relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-abs-word [off] 16-bit absolute section-crossing relocation
    Warns that a 16-bit absolute relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-rel-byte [off] 8-bit relative section-crossing relocation
    Warns that an 8-bit relative relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-rel-dword [off] 32-bit relative section-crossing relocation
    Warns that a 32-bit relative relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-rel-qword [off] 64-bit relative section-crossing relocation
    Warns that an 64-bit relative relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

reloc-rel-word [off] 16-bit relative section-crossing relocation
    Warns that a 16-bit relative relocation that could
    not be resolved at assembly time was generated in
    the output format.

    This is usually normal, but may not be handled by all
    possible target environments

section-alignment-rounded [on] section alignment rounded up
    Warn if a section alignment is specified which is
    not supported by the underlying object format, but
    can be rounded up to a supported value.

unknown-warning [off] unknown warning in \c{-W}/\c{-w} or warning directive
    Warns about a \c{-w} or \c{-W} option or a \c{[WARNING]} directive
    that contains an unknown warning name or is otherwise not possible
    to process.

user [on] \c{%warning} directives
    Controls output of \c{%warning} directives (see \k{pperror}).

warn-stack-empty [on] warning stack empty
    A \c{[WARNING POP]} directive was executed when
    the warning stack is empty. This is treated
    as a \c{[WARNING *all]} directive.

#
# This warning is currently issued by backends, but in the future
# that code should be centralized.
#
zeroing [on] \c{RES}\e{x} in initialized section becomes zero
    A \c{RES}\e{x} directive was used in a section which contains
    initialized data, and the output format does not support
    this. Instead, this will be replaced with explicit zero
    content, which may produce a large output file.

zext-reloc [on] relocation zero-extended to match output format
    Warns that a relocation has been zero-extended due
    to limitations in the output format.