https://gcc.gnu.org/g:35476a0da65fb13651238e38ae98398c78f12b2e
commit r16-6588-g35476a0da65fb13651238e38ae98398c78f12b2e Author: Jakub Jelinek <[email protected]> Date: Thu Jan 8 23:05:58 2026 +0100 stmt: Fix up parse_input_constraint [PR111817] The following invalid testcase ICEs, because we: 1) for some strange reason ignore invalid punctuations in parse_output_constraint, which has just default: if (!ISALPHA (*p)) break; compared to parse_input_constraint default: if (! ISALPHA (constraint[j])) { error ("invalid punctuation %qc in constraint", constraint[j]); return false; } Haven't touched this because I fear it could break real-world code 2) the checking whether = or + is first in the output constraint is a warning only: if (p != constraint) warning (0, "output constraint %qc for operand %d " "is not at the beginning", *p, operand_num); 3) parse_input_constraint parses also the corresponding output constraint if the input constraint has a number as the only variant, but even the comment removed in the following patch explains that it doesn't work correctly and skips the first character; now, usually that is not a big deal because if the first character of the output constraint is = or + as it should, then the checking doesn't do anything; but as 2) is just a warning, we accept it and then we fail to check it 4) far later on we parse the whole output constraint when input constraint refers to it and assert it succeeds, which it doesn't due to 1), 2) and 3) The following patch fixes the 3) spot, when switching to the output constraint, instead of setting j = 0; and break; (== continue;) so that it first does j += CONSTRAINT_LEN (constraint[0], constraint+0) and thus usually starts at second, sometimes third character of the output constraint it uses goto before the loop which sets j = 0; and doesn't do the j += ... 2026-01-08 Jakub Jelinek <[email protected]> PR middle-end/111817 * stmt.cc (parse_input_constraint): For matching construct, goto before the loop without changing j instead of break. Remove comment about that problem. * c-c++-common/pr111817.c: New test. Diff: --- gcc/stmt.cc | 8 ++------ gcc/testsuite/c-c++-common/pr111817.c | 9 +++++++++ 2 files changed, 11 insertions(+), 6 deletions(-) diff --git a/gcc/stmt.cc b/gcc/stmt.cc index b8b8d7975dd3..5816fb9b3b6e 100644 --- a/gcc/stmt.cc +++ b/gcc/stmt.cc @@ -508,6 +508,7 @@ parse_input_constraint (const char **constraint_p, int input_num, unsigned int alt = 0; unsigned long match = 0; +repeat: for (j = 0; j < c_len; j += CONSTRAINT_LEN (constraint[j], constraint+j)) switch (constraint[j]) { @@ -583,12 +584,7 @@ parse_input_constraint (const char **constraint_p, int input_num, constraint = constraints[match]; *constraint_p = constraint; c_len = strlen (constraint); - j = 0; - /* ??? At the end of the loop, we will skip the first part of - the matched constraint. This assumes not only that the - other constraint is an output constraint, but also that - the '=' or '+' come first. */ - break; + goto repeat; } else j = end - constraint; diff --git a/gcc/testsuite/c-c++-common/pr111817.c b/gcc/testsuite/c-c++-common/pr111817.c new file mode 100644 index 000000000000..637dbdadb8f0 --- /dev/null +++ b/gcc/testsuite/c-c++-common/pr111817.c @@ -0,0 +1,9 @@ +/* PR middle-end/111817 */ +/* { dg-do compile } */ + +int +foo (int x, int y) +{ + asm ("" : "\n=g" (x) : "0" (y)); /* { dg-warning "output constraint '=' for operand 0 is not at the beginning" } */ + return x; /* { dg-error "invalid punctuation '\\\\x\[0-9a-zA-Z]*' in constraint" "" { target *-*-* } .-1 } */ +}
