diff --git a/gcc/ChangeLog b/gcc/ChangeLog index e6a791c8c6a..6016aaaed54 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,14 @@ +2004-03-09 James E Wilson + + * alias.c (alias_sets_might_conflict_p): New. + * c-typeck.c (build_c_cast): Call it if warn_strict_aliasing > 1. + * common.opt (Wstrict-aliasing=): New. + * flags.h (warn_strict_aliasing): Change type to int. + * opts.c (warn_strict_aliasing): Change type to int. + (common_handle_option): Handle OPT_Wstrict_aliasing_. + * tree.h (alias_sets_might_conflict_p): Declare it. + * doc/invoke.tex (-Wstrict-aliasing=2): Document it. + 2004-03-10 Roman Zippel PR bootstrap/12371 diff --git a/gcc/alias.c b/gcc/alias.c index d670a7db19e..30013ec7d6a 100644 --- a/gcc/alias.c +++ b/gcc/alias.c @@ -290,6 +290,19 @@ alias_sets_conflict_p (HOST_WIDE_INT set1, HOST_WIDE_INT set2) child of the other. Therefore, they cannot alias. */ return 0; } + +/* Return 1 if the two specified alias sets might conflict, or if any subtype + of these alias sets might conflict. */ + +int +alias_sets_might_conflict_p (HOST_WIDE_INT set1, HOST_WIDE_INT set2) +{ + if (set1 == 0 || set2 == 0 || set1 == set2) + return 1; + + return 0; +} + /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has has any readonly fields. If any of the fields have types that diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c index a49b5ea2898..f23fac78342 100644 --- a/gcc/c-typeck.c +++ b/gcc/c-typeck.c @@ -3027,10 +3027,17 @@ build_c_cast (tree type, tree expr) if the cast breaks type based aliasing. */ if (!COMPLETE_TYPE_P (TREE_TYPE (type))) warning ("type-punning to incomplete type might break strict-aliasing rules"); - else if (!alias_sets_conflict_p - (get_alias_set (TREE_TYPE (TREE_OPERAND (expr, 0))), - get_alias_set (TREE_TYPE (type)))) - warning ("dereferencing type-punned pointer will break strict-aliasing rules"); + else + { + HOST_WIDE_INT set1 = get_alias_set (TREE_TYPE (TREE_OPERAND (expr, 0))); + HOST_WIDE_INT set2 = get_alias_set (TREE_TYPE (type)); + + if (!alias_sets_conflict_p (set1, set2)) + warning ("dereferencing type-punned pointer will break strict-aliasing rules"); + else if (warn_strict_aliasing > 1 + && !alias_sets_might_conflict_p (set1, set2)) + warning ("dereferencing type-punned pointer might break strict-aliasing rules"); + } } /* If pedantic, warn for conversions between function and object diff --git a/gcc/common.opt b/gcc/common.opt index d9faa60a8f5..f1a045316e4 100644 --- a/gcc/common.opt +++ b/gcc/common.opt @@ -104,6 +104,10 @@ Wstrict-aliasing Common Warn about code which might break strict aliasing rules +Wstrict-aliasing= +Common Joined UInteger +Warn about code which might break strict aliasing rules + Wswitch Common Warn about enumerated switches, with no default, missing a case diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 8caed2b1978..0c9f183387f 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -226,7 +226,7 @@ in the following sections. -Wno-multichar -Wnonnull -Wpacked -Wpadded @gol -Wparentheses -Wpointer-arith -Wredundant-decls @gol -Wreturn-type -Wsequence-point -Wshadow @gol --Wsign-compare -Wstrict-aliasing @gol +-Wsign-compare -Wstrict-aliasing -Wstrict-aliasing=2 @gol -Wswitch -Wswitch-default -Wswitch-enum @gol -Wsystem-headers -Wtrigraphs -Wundef -Wuninitialized @gol -Wunknown-pragmas -Wunreachable-code @gol @@ -2449,6 +2449,13 @@ compiler is using for optimization. The warning does not catch all cases, but does attempt to catch the more common pitfalls. It is included in @option{-Wall}. +@item -Wstrict-aliasing=2 +@opindex Wstrict-aliasing=2 +This option is only active when @option{-fstrict-aliasing} is active. +It warns about all code which might break the strict aliasing rules that the +compiler is using for optimization. This warning catches all cases, but +it will also give a warning for some ambiguous cases that are safe. + @item -Wall @opindex Wall All of the above @samp{-W} options combined. This enables all the diff --git a/gcc/flags.h b/gcc/flags.h index b088f6cb3ba..8a70fc31b78 100644 --- a/gcc/flags.h +++ b/gcc/flags.h @@ -184,7 +184,7 @@ extern bool warn_deprecated_decl; /* Nonzero means warn about constructs which might not be strict aliasing safe. */ -extern bool warn_strict_aliasing; +extern int warn_strict_aliasing; /* Nonzero if generating code to do profiling. */ diff --git a/gcc/opts.c b/gcc/opts.c index fa1971cd651..99d576a3af8 100644 --- a/gcc/opts.c +++ b/gcc/opts.c @@ -100,7 +100,7 @@ bool warn_shadow; /* Nonzero means warn about constructs which might not be strict-aliasing safe. */ -bool warn_strict_aliasing; +int warn_strict_aliasing; /* True to warn if a switch on an enum, that does not have a default case, fails to have a case for every enum value. */ @@ -747,6 +747,7 @@ common_handle_option (size_t scode, const char *arg, break; case OPT_Wstrict_aliasing: + case OPT_Wstrict_aliasing_: warn_strict_aliasing = value; break; diff --git a/gcc/tree.h b/gcc/tree.h index 0a1e3fb0bd6..6af6c662ff0 100644 --- a/gcc/tree.h +++ b/gcc/tree.h @@ -2887,6 +2887,7 @@ extern tree strip_float_extensions (tree); extern void record_component_aliases (tree); extern HOST_WIDE_INT get_alias_set (tree); extern int alias_sets_conflict_p (HOST_WIDE_INT, HOST_WIDE_INT); +extern int alias_sets_might_conflict_p (HOST_WIDE_INT, HOST_WIDE_INT); extern int readonly_fields_p (tree); extern int objects_must_conflict_p (tree, tree);