NASM - The Netwide Assembler

Appendix A: List of Warning Classes

These are the warning classes currently defined by NASM for the purpose of enabling, disabling and promoting to error. See section 2.1.26 and section 8.14.

• all: all possible warnings

  all is an group alias for all warning classes. Thus, -w+all enables all available warnings, and -w-all disables warnings entirely (since NASM 2.13).

• bad-pragma: malformed %pragma

  bad-pragma is a backwards compatibility alias for pragma-bad.

• bnd: invalid BND prefix

  bnd is a backwards compatibility alias for prefix-bnd.

• db-empty: no operand for data declaration

  db-empty warns about a Dx declaration with no operands, producing no output. This is permitted, but often indicative of an error. See section 3.2.1.

  Enabled by default.

• ea: all ea- warnings

  ea is a group alias for all warning classes prefixed by ea-; currently ea-absolute and ea-dispsize.

• ea-absolute: absolute address cannot be RIP-relative

  ea-absolute warns that an address that is inherently absolute cannot be generated with RIP-relative encoding using REL, see section 8.2.1.

  Enabled by default.

• ea-dispsize: displacement size ignored on absolute address

  ea-dispsize warns that NASM does not support generating displacements for inherently absolute addresses that do not match the address size of the instruction.

  Enabled by default.

• environment: nonexistent environment variable

  environment is a backwards compatibility alias for pp-environment.

• float: all float- warnings

  float is a group alias for all warning classes prefixed by float-; currently float-denorm, float-overflow, float-toolong, float-underflow.

• float-denorm: floating point denormal

  float-denorm warns about denormal floating point constants.

  Disabled by default.

• float-overflow: floating point overflow

  float-overflow warns about floating point underflow.

  Enabled by default.

• float-toolong: too many digits in floating-point number

  float-toolong warns about too many digits in floating-point numbers.

  Enabled by default.

• float-underflow: floating point underflow

  float-underflow warns about floating point underflow (a nonzero constant rounded to zero.)

  Disabled by default.

• forward: forward reference may have unpredictable results

  forward warns that a forward reference is used which may have unpredictable results, notably in a RESB–type pseudo-instruction. These would be critical expressions (see section 3.8) 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.

  Enabled by default.

• hle: invalid HLE prefix

  hle is a backwards compatibility alias for prefix-hle.

• implicit-abs-deprecated: implicit DEFAULT ABS is deprecated

  implicit-abs-deprecated warns that in a subsequent version of NASM, the 64-bit default addressing form is likely to change from DEFAULT ABS to DEFAULT REL. If absolute addressing is indeed intended, it is strongly recommended to specify DEFAULT ABS explicitly.

  Enabled by default.

• label: all label- warnings

  label is a group alias for all warning classes prefixed by label-; currently label-orphan, label-redef, label-redef-late.

• label-orphan: labels alone on lines without trailing :

  label-orphan 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 section 3.1.)

  Enabled by default.

• label-redef: label redefined to an identical value

  label-redef 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 different values.

  Disabled by default.

• label-redef-late: label (re)defined during code generation

  label-redef-late 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.

  Enabled and promoted to error by default.

• lock: LOCK prefix on unlockable instruction

  lock is a backwards compatibility alias for prefix-lock-error.

• macro-def-case-single: single-line macro defined both case sensitive and insensitive

  macro-def-case-single is a backwards compatibility alias for pp-macro-def-case-single.

• macro-def-greedy-single: single-line macro

  macro-def-greedy-single is a backwards compatibility alias for pp-macro-def-greedy-single.

• macro-def-param-single: single-line macro defined with and without parameters

  macro-def-param-single is a backwards compatibility alias for pp-macro-def-param-single.

• macro-defaults: macros with more default than optional parameters

  macro-defaults is a backwards compatibility alias for pp-macro-defaults.

• macro-params-legacy: improperly calling multi-line macro for legacy support

  macro-params-legacy is a backwards compatibility alias for pp-macro-params-legacy.

• macro-params-multi: multi-line macro calls with wrong parameter count

  macro-params-multi is a backwards compatibility alias for pp-macro-params-multi.

• macro-params-single: single-line macro calls with wrong parameter count

  macro-params-single is a backwards compatibility alias for pp-macro-params-single.

• negative-rep: regative %rep count

  negative-rep is a backwards compatibility alias for pp-rep-negative.

• not-my-pragma: %pragma not applicable to this compilation

  not-my-pragma is a backwards compatibility alias for pragma-na.

• number: all number- warnings

  number is a group alias for all warning classes prefixed by number-; currently number-deprecated-hex and number-overflow.

• number-deprecated-hex: $ prefix for hexadecimal is deprecated

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

  Enabled by default.

• number-overflow: numeric constant does not fit

  number-overflow covers warnings about numeric constants which don't fit in 64 bits.

  Enabled by default.

• obsolete: all obsolete- warnings

  obsolete is a group alias for all warning classes prefixed by obsolete-; currently obsolete-nop, obsolete-removed, obsolete-valid.

• obsolete-nop: instruction obsolete and is a noop on the target CPU

  obsolete-nop warns for an instruction which has been removed from the architecture, but has been architecturally defined to be a noop for future CPUs.

  Enabled by default.

• obsolete-removed: instruction obsolete and removed on the target CPU

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

  Enabled by default.

• obsolete-valid: instruction obsolete but valid on the target CPU

  obsolete-valid warns for an instruction which has been removed from the architecture, but is still valid on the specific CPU given in the CPU directive. Code using these instructions is most likely not forward compatible.

  Enabled by default.

• orphan-labels: labels alone on lines without trailing :

  orphan-labels is a backwards compatibility alias for label-orphan.

• other: any warning not specifically mentioned above

  other specifies any warning not included in any specific warning class.

  Enabled by default.

• phase: phase error during stabilization

  phase 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.

  Disabled by default.

• pp: all pp- warnings

  pp is a group alias for all warning classes prefixed by pp-; currently pp-else-elif, pp-else-else, pp-empty-braces, pp-environment, pp-macro-def-case-single, pp-macro-def-greedy-single, pp-macro-def-param-single, pp-macro-defaults, pp-macro-params-legacy, pp-macro-params-multi, pp-macro-params-single, pp-macro-redef-multi, pp-open-braces, pp-open-brackets, pp-open-string, pp-rep-negative, pp-sel-range, pp-trailing.

• pp-else: all pp-else- warnings

  pp-else is a group alias for all warning classes prefixed by pp-else-; currently pp-else-elif and pp-else-else.

• pp-else-elif: %elif after %else

  pp-else-elif warns that an %elif–type directive was encountered after %else has already been encounted. As a result, the content of the %elif will never be expanded.

  Enabled by default.

• pp-else-else: %else after %else

  pp-else-else warns that a second %else clause was found for the same %if statement. The content of this %else clause will never be expanded.

  Enabled by default.

• pp-empty-braces: empty %{} construct

  pp-empty-braces warns that an empty %{} was encountered. This expands to a single % character, which is normally the % arithmetic operator.

  Enabled by default.

• pp-environment: nonexistent environment variable

  pp-environment warns if a nonexistent environment variable is accessed using the %! preprocessor construct (see section 5.13.2.) 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.

  Enabled by default.

• pp-macro: all pp-macro- warnings

  pp-macro is a group alias for all warning classes prefixed by pp-macro-; currently pp-macro-def-case-single, pp-macro-def-greedy-single, pp-macro-def-param-single, pp-macro-defaults, pp-macro-params-legacy, pp-macro-params-multi, pp-macro-params-single, pp-macro-redef-multi.

• pp-macro-def: all pp-macro-def- warnings

  pp-macro-def is a group alias for all warning classes prefixed by pp-macro-def-; currently pp-macro-def-case-single, pp-macro-def-greedy-single, pp-macro-def-param-single.

• pp-macro-def-case-single: single-line macro defined both case sensitive and insensitive

  pp-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 %undef, or, if the original macro is the case insensitive one, the macro call is done with a different case.

  Enabled by default.

• pp-macro-def-greedy-single: single-line macro

  pp-macro-def-greedy-single definition shadows greedy macro warns when 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 %undef, and will be invoked if called with a parameter count that does not match the new definition.

  Enabled by default.

• pp-macro-def-param-single: single-line macro defined with and without parameters

  pp-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 %undef.

  Enabled and promoted to error by default.

• pp-macro-defaults: macros with more default than optional parameters

  pp-macro-defaults warns when a macro has more default parameters than optional parameters. See section 5.5.5 for why might want to disable this warning.

  Enabled by default.

• pp-macro-params: all pp-macro-params- warnings

  pp-macro-params is a group alias for all warning classes prefixed by pp-macro-params-; currently pp-macro-params-legacy, pp-macro-params-multi, pp-macro-params-single.

• pp-macro-params-legacy: improperly calling multi-line macro for legacy support

  pp-macro-params-legacy warns about 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:

       %pragma preproc sane_empty_expansion true
  

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

  Enabled by default.

• pp-macro-params-multi: multi-line macro calls with wrong parameter count

  pp-macro-params-multi warns about multi-line macros being invoked with the wrong number of parameters. See section 5.5.1 for an example of why you might want to disable this warning.

  Enabled by default.

• pp-macro-params-single: single-line macro calls with wrong parameter count

  pp-macro-params-single warns about single-line macros being invoked with the wrong number of parameters.

  Enabled by default.

• pp-macro-redef-multi: redefining multi-line macro

  pp-macro-redef-multi warns that a multi-line macro is being redefined, without first removing the old definition with %unmacro.

  Enabled by default.

• pp-open: all pp-open- warnings

  pp-open is a group alias for all warning classes prefixed by pp-open-; currently pp-open-braces, pp-open-brackets, pp-open-string.

• pp-open-braces: unterminated %{...}

  pp-open-braces warns that a preprocessor parameter enclosed in braces %{...} lacks the terminating } character.

  Enabled by default.

• pp-open-brackets: unterminated %[...]

  pp-open-brackets warns that a preprocessor %[...] construct lacks the terminating ] character.

  Enabled by default.

• pp-open-string: unterminated string

  pp-open-string warns that a quoted string without a closing quotation mark was encountered during preprocessing.

  Enabled by default.

• pp-rep-negative: regative %rep count

  pp-rep-negative warns about a negative count given to the %rep preprocessor directive.

  Enabled by default.

• pp-sel-range: %sel() argument out of range

  pp-sel-range warns that the %sel() preprocessor function was passed a value less than 1 or larger than the number of available arguments.

  Enabled by default.

• pp-trailing: trailing garbage ignored

  pp-trailing 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.

  Enabled by default.

• pragma: all pragma- warnings

  pragma is a group alias for all warning classes prefixed by pragma-; currently pragma-bad, pragma-empty, pragma-na, pragma-unknown.

• pragma-bad: malformed %pragma

  pragma-bad warns about a malformed or otherwise unparsable %pragma directive.

  Disabled by default.

• pragma-empty: empty %pragma directive

  pragma-empty warns about a %pragma directive containing nothing. This is treated identically to %pragma ignore except for this optional warning.

  Disabled by default.

• pragma-na: %pragma not applicable to this compilation

  pragma-na warns about a %pragma directive which is not applicable to this particular assembly session. This is not yet implemented.

  Disabled by default.

• pragma-unknown: unknown %pragma facility or directive

  pragma-unknown warns about an unknown %pragma directive. This is not yet implemented for most cases.

  Disabled by default.

• prefix: all prefix- warnings

  prefix is a group alias for all warning classes prefixed by prefix-; currently prefix-bnd, prefix-hint-dropped, prefix-hle, prefix-invalid, prefix-lock-error, prefix-lock-xchg, prefix-opsize, prefix-seg.

• prefix-bnd: invalid BND prefix

  prefix-bnd warns about ineffective use of the BND prefix when the JMP instruction is converted to the SHORT form. This should be extremely rare since the short JMP only is applicable to jumps inside the same module, but if it is legitimate, it may be necessary to use bnd jmp dword.

  Enabled by default.

• prefix-hint-dropped: invalid branch hint prefix dropped

  prefix-hint-dropped warns that the {PT} (predict taken) or {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 DS or CS, instead, respectively.

  Enabled by default.

• prefix-hle: invalid HLE prefix

  prefix-hle warns about invalid use of the HLE XACQUIRE or XRELEASE prefixes.

  Enabled by default.

• prefix-invalid: invalid prefix for instruction

  prefix-invalid this instruction 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.

  Enabled by default.

• prefix-lock: all prefix-lock- warnings

  prefix-lock is a group alias for all warning classes prefixed by prefix-lock-; currently prefix-lock-error and prefix-lock-xchg.

• prefix-lock-error: LOCK prefix on unlockable instruction

  prefix-lock-error warns about LOCK prefixes on unlockable instructions.

  Enabled by default.

• prefix-lock-xchg: superfluous LOCK prefix on XCHG instruction

  prefix-lock-xchg warns about a LOCK prefix added to an XCHG instruction. The XCHG instruction is 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.

  Enabled by default.

• prefix-opsize: invalid operand size prefix

  prefix-opsize warns that an operand prefix (o16, o32, o64, osp) invalid for the specified instruction has been specified. The operand prefix will be ignored by the assembler.

  Enabled by default.

• prefix-seg: segment prefix ignored in 64-bit mode

  prefix-seg warns that an es, cs, ss or ds segment override prefix has no effect in 64-bit mode. The prefix will still be generated as requested.

  Enabled by default.

• ptr: non-NASM keyword used in other assemblers

  ptr warns about keywords used in other assemblers that might indicate a mistake in the source code. Currently only the MASM PTR keyword is recognized. If (limited) MASM compatibility is desired, the %use masm macro package is available, see section 7.5; however, carefully note the caveats listed.

  Enabled by default.

• regsize: register size specification ignored

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

       KMOVW K0,[foo]          ; Permitted, KMOVW implies 16 bits 
       KMOV  WORD K0,[foo]     ; Permitted, WORD K0 specifies instruction size 
       KMOV  K0,WORD [foo]     ; Permitted, WORD [foo] specifies instruction size 
       KMOV  K0,[foo]          ; Not permitted, instruction size ambiguous
  

  Enabled by default.

• reloc: all reloc- warnings

  reloc is a group alias for all warning classes prefixed by reloc-; currently reloc-abs-byte, reloc-abs-dword, reloc-abs-qword, reloc-abs-word, reloc-rel-byte, reloc-rel-dword, reloc-rel-qword, reloc-rel-word.

• reloc-abs: all reloc-abs- warnings

  reloc-abs is a group alias for all warning classes prefixed by reloc-abs-; currently reloc-abs-byte, reloc-abs-dword, reloc-abs-qword, reloc-abs-word.

• reloc-abs-byte: 8-bit absolute section-crossing relocation

  reloc-abs-byte 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

  Disabled by default.

• reloc-abs-dword: 32-bit absolute section-crossing relocation

  reloc-abs-dword 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

  Disabled by default.

• reloc-abs-qword: 64-bit absolute section-crossing relocation

  reloc-abs-qword 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

  Disabled by default.

• reloc-abs-word: 16-bit absolute section-crossing relocation

  reloc-abs-word 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

  Disabled by default.

• reloc-rel: all reloc-rel- warnings

  reloc-rel is a group alias for all warning classes prefixed by reloc-rel-; currently reloc-rel-byte, reloc-rel-dword, reloc-rel-qword, reloc-rel-word.

• reloc-rel-byte: 8-bit relative section-crossing relocation

  reloc-rel-byte 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

  Disabled by default.

• reloc-rel-dword: 32-bit relative section-crossing relocation

  reloc-rel-dword 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

  Disabled by default.

• reloc-rel-qword: 64-bit relative section-crossing relocation

  reloc-rel-qword 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

  Disabled by default.

• reloc-rel-word: 16-bit relative section-crossing relocation

  reloc-rel-word 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

  Disabled by default.

• section-alignment-rounded: section alignment rounded up

  section-alignment-rounded 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.

  Enabled by default.

• unknown-pragma: unknown %pragma facility or directive

  unknown-pragma is a backwards compatibility alias for pragma-unknown.

• unknown-warning: unknown warning in -W/-w or warning directive

  unknown-warning warns about a -w or -W option or a [WARNING] directive that contains an unknown warning name or is otherwise not possible to process.

  Disabled by default.

• user: %warning directives

  user controls output of %warning directives (see section 5.11).

  Enabled by default.

• warn-stack-empty: warning stack empty

  warn-stack-empty a [WARNING POP] directive was executed when the warning stack is empty. This is treated as a [WARNING *all] directive.

  Enabled by default.

• zeroing: RESx in initialized section becomes zero

  zeroing a RESx 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.

  Enabled by default.

• zext-reloc: relocation zero-extended to match output format

  zext-reloc warns that a relocation has been zero-extended due to limitations in the output format.

  Enabled by default.