diff options
Diffstat (limited to 'gcc/doc/invoke.texi')
| -rw-r--r-- | gcc/doc/invoke.texi | 58 |
1 files changed, 43 insertions, 15 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 492ca29..f93fe43 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -272,7 +272,7 @@ in the following sections. -Woverloaded-virtual -Wno-pmf-conversions -Wself-move -Wsign-promo -Wsized-deallocation -Wsuggest-final-methods -Wsuggest-final-types -Wsuggest-override -Wno-template-body --Wno-template-id-cdtor -Wtemplate-names-tu-local +-Wno-template-id-cdtor -Wtemplate-names-tu-local -Wno-external-tu-local -Wno-terminate -Wno-vexing-parse -Wvirtual-inheritance -Wno-virtual-move-assign -Wvolatile} @@ -4759,6 +4759,32 @@ The presence of an explicit instantiation silences the warning. This flag is enabled by @option{-Wextra}. +@opindex Wexternal-tu-local +@opindex Wno-external-tu-local +@item -Wno-external-tu-local +Warn when naming a TU-local entity outside of the translation unit it +was declared in. Such declarations will be ignored during name lookup. +This can occur when performing ADL from a template declared in the same +TU as the internal function: + +@smallexample +export module M; +template <typename T> void foo(T t) @{ + bar(t); +@} +struct S @{@} s; +static void bar(S) @{@} // internal linkage + +// instantiating foo(s) from outside this TU can see ::bar, +// but naming it there is ill-formed. +@end smallexample + +This can be worked around by making @code{bar} attached to the global +module, using @code{extern "C++"}. + +This warning is enabled by default, and is upgraded to an error by +@option{-pedantic-errors}. + @opindex Wterminate @opindex Wno-terminate @item -Wno-terminate @r{(C++ and Objective-C++ only)} @@ -14725,27 +14751,25 @@ and @option{-fauto-profile}. @opindex ftrivial-auto-var-init @item -ftrivial-auto-var-init=@var{choice} -Initialize automatic variables with either a pattern or with zeroes to increase -the security and predictability of a program by preventing uninitialized memory -disclosure and use. +Initialize automatic variables or temporary objects with either a pattern or with +zeroes to increase the security and predictability of a program by preventing +uninitialized memory disclosure and use. GCC still considers an automatic variable that doesn't have an explicit initializer as uninitialized, @option{-Wuninitialized} and @option{-Wanalyzer-use-of-uninitialized-value} will still report -warning messages on such automatic variables and the compiler will -perform optimization as if the variable were uninitialized. +warning messages on such automatic variables or temporary objects and the +compiler will perform optimization as if the variable were uninitialized. With this option, GCC will also initialize any padding of automatic variables -that have structure or union types to zeroes. -However, the current implementation cannot initialize automatic variables that -are declared between the controlling expression and the first case of a -@code{switch} statement. Using @option{-Wtrivial-auto-var-init} to report all -such cases. +or temporary objects that have structure or union types to zeroes. +However, the current implementation cannot initialize automatic variables +whose initialization is bypassed through @code{switch} or @code{goto} +statement. Using @option{-Wtrivial-auto-var-init} to report all such cases. The three values of @var{choice} are: @itemize @bullet @item @samp{uninitialized} doesn't initialize any automatic variables. -This is C and C++'s default. @item @samp{pattern} Initialize automatic variables with values which will likely @@ -14759,7 +14783,10 @@ The values used for pattern initialization might be changed in the future. @samp{zero} Initialize automatic variables with zeroes. @end itemize -The default is @samp{uninitialized}. +The default is @samp{uninitialized} except for C++26, in which case +if @option{-ftrivial-auto-var-init=} is not specified at all automatic +variables or temporary objects are zero initialized, but zero initialization +of padding bits does not happen. Note that the initializer values, whether @samp{zero} or @samp{pattern}, refer to data representation (in memory or machine registers), rather @@ -14772,7 +14799,7 @@ with the bit patterns @code{0x00} or @code{0xFE}, depending on @var{choice}, whether or not these representations stand for values in that range, and even if they do, the interpretation of the value held by the variable will depend on the bias. A @samp{hardbool} variable that -uses say @code{0X5A} and @code{0xA5} for @code{false} and @code{true}, +uses say @code{0x5A} and @code{0xA5} for @code{false} and @code{true}, respectively, will trap with either @samp{choice} of trivial initializer, i.e., @samp{zero} initialization will not convert to the representation for @code{false}, even if it would for a @code{static} @@ -14783,7 +14810,8 @@ are initialized with @code{false} (zero), even when @samp{pattern} is requested. You can control this behavior for a specific variable by using the variable -attribute @code{uninitialized} (@pxref{Variable Attributes}). +attribute @code{uninitialized} standard attribute (@pxref{Variable Attributes}) +or the C++26 @code{[[indeterminate]]}. @opindex fvect-cost-model @item -fvect-cost-model=@var{model} |