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Diffstat (limited to 'gcc/diagnostics/macro-unwinding.cc')
| -rw-r--r-- | gcc/diagnostics/macro-unwinding.cc | 227 |
1 files changed, 227 insertions, 0 deletions
diff --git a/gcc/diagnostics/macro-unwinding.cc b/gcc/diagnostics/macro-unwinding.cc new file mode 100644 index 0000000..66bad1c --- /dev/null +++ b/gcc/diagnostics/macro-unwinding.cc @@ -0,0 +1,227 @@ +/* Code for unwinding macro expansions in diagnostics. + Copyright (C) 1999-2025 Free Software Foundation, Inc. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it under +the terms of the GNU General Public License as published by the Free +Software Foundation; either version 3, or (at your option) any later +version. + +GCC is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +<http://www.gnu.org/licenses/>. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tree.h" +#include "diagnostic.h" +#include "diagnostics/macro-unwinding.h" +#include "diagnostics/text-sink.h" +#include "intl.h" + +namespace diagnostics { + +/* This is a pair made of a location and the line map it originated + from. It's used in the maybe_unwind_expanded_macro_loc function + below. */ +struct loc_map_pair +{ + const line_map_macro *map; + location_t where; +}; + + +/* Unwind the different macro expansions that lead to the token which + location is WHERE and emit diagnostics showing the resulting + unwound macro expansion trace. Let's look at an example to see how + the trace looks like. Suppose we have this piece of code, + artificially annotated with the line numbers to increase + legibility: + + $ cat -n test.c + 1 #define OPERATE(OPRD1, OPRT, OPRD2) \ + 2 OPRD1 OPRT OPRD2; + 3 + 4 #define SHIFTL(A,B) \ + 5 OPERATE (A,<<,B) + 6 + 7 #define MULT(A) \ + 8 SHIFTL (A,1) + 9 + 10 void + 11 g () + 12 { + 13 MULT (1.0);// 1.0 << 1; <-- so this is an error. + 14 } + + Here is the diagnostic that we want the compiler to generate: + + test.c: In function ‘g’: + test.c:5:14: error: invalid operands to binary << (have ‘double’ and ‘int’) + test.c:2:9: note: in definition of macro 'OPERATE' + test.c:8:3: note: in expansion of macro 'SHIFTL' + test.c:13:3: note: in expansion of macro 'MULT' + + The part that goes from the third to the fifth line of this + diagnostic (the lines containing the 'note:' string) is called the + unwound macro expansion trace. That's the part generated by this + function. */ + +void +maybe_unwind_expanded_macro_loc (text_sink &text_output, + location_t where) +{ + const struct line_map *map; + auto_vec<loc_map_pair> loc_vec; + unsigned ix; + loc_map_pair loc, *iter; + + const location_t original_loc = where; + + map = linemap_lookup (line_table, where); + if (!linemap_macro_expansion_map_p (map)) + return; + + /* Let's unwind the macros that got expanded and led to the token + which location is WHERE. We are going to store these macros into + LOC_VEC, so that we can later walk it at our convenience to + display a somewhat meaningful trace of the macro expansion + history to the user. Note that the first macro of the trace + (which is OPERATE in the example above) is going to be stored at + the beginning of LOC_VEC. */ + + do + { + loc.where = where; + loc.map = linemap_check_macro (map); + + loc_vec.safe_push (loc); + + /* WHERE is the location of a token inside the expansion of a + macro. MAP is the map holding the locations of that macro + expansion. Let's get the location of the token inside the + context that triggered the expansion of this macro. + This is basically how we go "down" in the trace of macro + expansions that led to WHERE. */ + where = linemap_unwind_toward_expansion (line_table, where, &map); + } while (linemap_macro_expansion_map_p (map)); + + /* Now map is set to the map of the location in the source that + first triggered the macro expansion. This must be an ordinary map. */ + const line_map_ordinary *ord_map = linemap_check_ordinary (map); + + /* Walk LOC_VEC and print the macro expansion trace, unless the + first macro which expansion triggered this trace was expanded + inside a system header. */ + int saved_location_line = + expand_location_to_spelling_point (original_loc).line; + + if (!LINEMAP_SYSP (ord_map)) + FOR_EACH_VEC_ELT (loc_vec, ix, iter) + { + /* Sometimes, in the unwound macro expansion trace, we want to + print a part of the context that shows where, in the + definition of the relevant macro, is the token (we are + looking at) used. That is the case in the introductory + comment of this function, where we print: + + test.c:2:9: note: in definition of macro 'OPERATE'. + + We print that "macro definition context" because the + diagnostic line (emitted by the call to + pp_ouput_formatted_text in diagnostic_report_diagnostic): + + test.c:5:14: error: invalid operands to binary << (have ‘double’ and ‘int’) + + does not point into the definition of the macro where the + token '<<' (that is an argument to the function-like macro + OPERATE) is used. So we must "display" the line of that + macro definition context to the user somehow. + + A contrario, when the first interesting diagnostic line + points into the definition of the macro, we don't need to + display any line for that macro definition in the trace + anymore, otherwise it'd be redundant. */ + + /* Okay, now here is what we want. For each token resulting + from macro expansion we want to show: 1/ where in the + definition of the macro the token comes from; 2/ where the + macro got expanded. */ + + /* Resolve the location iter->where into the locus 1/ of the + comment above. */ + location_t resolved_def_loc = + linemap_resolve_location (line_table, iter->where, + LRK_MACRO_DEFINITION_LOCATION, nullptr); + + /* Don't print trace for locations that are reserved or from + within a system header. */ + const line_map_ordinary *m = nullptr; + location_t l = + linemap_resolve_location (line_table, resolved_def_loc, + LRK_SPELLING_LOCATION, &m); + location_t l0 = l; + if (IS_ADHOC_LOC (l0)) + l0 = get_location_from_adhoc_loc (line_table, l0); + if (l0 < RESERVED_LOCATION_COUNT || LINEMAP_SYSP (m)) + continue; + + /* We need to print the context of the macro definition only + when the locus of the first displayed diagnostic (displayed + before this trace) was inside the definition of the + macro. */ + const int resolved_def_loc_line = SOURCE_LINE (m, l0); + if (ix == 0 && saved_location_line != resolved_def_loc_line) + { + text_output.append_note (resolved_def_loc, + "in definition of macro %qs", + linemap_map_get_macro_name (iter->map)); + /* At this step, as we've printed the context of the macro + definition, we don't want to print the context of its + expansion, otherwise, it'd be redundant. */ + continue; + } + + /* Resolve the location of the expansion point of the macro + which expansion gave the token represented by def_loc. + This is the locus 2/ of the earlier comment. */ + location_t resolved_exp_loc = + linemap_resolve_location (line_table, + iter->map->get_expansion_point_location (), + LRK_MACRO_DEFINITION_LOCATION, nullptr); + + text_output.append_note (resolved_exp_loc, + "in expansion of macro %qs", + linemap_map_get_macro_name (iter->map)); + } +} + +/* This is a diagnostic finalizer implementation that is aware of + virtual locations produced by libcpp. + + It has to be called by the diagnostic finalizer of front ends that + uses libcpp and wish to get diagnostics involving tokens resulting + from macro expansion. + + For a given location, if said location belongs to a token + resulting from a macro expansion, this starter prints the context + of the token. E.g, for multiply nested macro expansion, it + unwinds the nested macro expansions and prints them in a manner + that is similar to what is done for function call stacks, or + template instantiation contexts. */ +void +virt_loc_aware_text_finalizer (text_sink &text_output, + const diagnostic_info *diagnostic) +{ + maybe_unwind_expanded_macro_loc (text_output, + diagnostic_location (diagnostic)); +} + +} // namespace diagnostics |