Compilation errors with gcc 8.5

[eregon]

From https://github.com/truffleruby/truffleruby/actions/runs/23622289219/job/68803953288#step:5:2166

#14 196.3 compiling build/shared/serialize.o
#14 196.3 src/prism.c: In function ‘parse_arguments’:
#14 196.3 src/prism.c:13891:189: error: conversion from ‘unsigned int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3                      argument = parse_value_expression(parser, PM_BINDING_POWER_DEFINED, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (!parsed_first_argument ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0u) | PM_PARSE_ACCEPTS_LABEL, PM_ERR_EXPECT_ARGUMENT, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                                                                              ^
#14 196.3 src/prism.c: In function ‘parse_case’:
#14 196.3 src/prism.c:17795:118: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3          predicate = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CASE_EXPRESSION_AFTER_CASE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                       ^
#14 196.3 src/prism.c:17914:137: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3                  pm_node_t *predicate = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_IF_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                          ^
#14 196.3 src/prism.c:17918:137: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3                  pm_node_t *predicate = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_UNLESS_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                          ^
#14 196.3 src/prism.c: In function ‘parse_class’:
#14 196.3 src/prism.c:18007:130: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3          pm_node_t *expression = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_EXPECT_EXPRESSION_AFTER_LESS_LESS, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                   ^
#14 196.3 src/prism.c:18056:119: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3          superclass = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CLASS_SUPERCLASS, (uint16_t) (depth + 1));
#14 196.3                                                                                                                        ^
#14 196.3 src/prism.c: In function ‘parse_def’:
#14 196.3 src/prism.c:18238:134: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *expression = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_DEF_RECEIVER, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                       ^
#14 196.3 src/prism.c: In function ‘parse_expression_prefix’:
#14 196.3 src/prism.c:19124:124: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3                      element = parse_value_expression(parser, PM_BINDING_POWER_DEFINED, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_LABEL, PM_ERR_ARRAY_EXPRESSION, (uint16_t) (depth + 1));
#14 196.3                                                                                                                             ^
#14 196.3 src/prism.c:19854:134: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *collection = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_FOR_COLLECTION, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                       ^
#14 196.3 src/prism.c:19957:111: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3                  receiver = parse_expression(parser, PM_BINDING_POWER_NOT, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_NOT_EXPRESSION, (uint16_t) (depth + 1));
#14 196.3                                                                                                                ^
#14 196.3 src/prism.c:20003:133: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *predicate = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_UNTIL_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                      ^
#14 196.3 src/prism.c:20036:133: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *predicate = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_WHILE_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                                      ^
#14 196.3 src/prism.c:20370:144: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *receiver = parse_expression(parser, pm_binding_powers[parser->previous.type].right, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (binding_power < PM_BINDING_POWER_MATCH ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0), PM_ERR_UNARY_RECEIVER, (uint16_t) (depth + 1));
#14 196.3                                                                                                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#14 196.3 src/prism.c: In function ‘parse_assignment_value’:
#14 196.3 src/prism.c:20571:106: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3      pm_node_t *value = parse_value_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (previous_binding_power == PM_BINDING_POWER_ASSIGNMENT ? (flags & PM_PARSE_ACCEPTS_COMMAND_CALL) : (previous_binding_power < PM_BINDING_POWER_MATCH ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0)), diag_id, (uint16_t) (depth + 1));
#14 196.3                                                                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#14 196.3 src/prism.c: In function ‘parse_assignment_values’:
#14 196.3 src/prism.c:20653:108: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3      pm_node_t *value = parse_starred_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (previous_binding_power == PM_BINDING_POWER_ASSIGNMENT ? (flags & PM_PARSE_ACCEPTS_COMMAND_CALL) : (previous_binding_power < PM_BINDING_POWER_MODIFIER ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0)), diag_id, (uint16_t) (depth + 1));
#14 196.3                                                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#14 196.3 src/prism.c:20708:148: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3          pm_node_t *right = parse_expression(parser, pm_binding_powers[PM_TOKEN_KEYWORD_RESCUE_MODIFIER].right, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (accepts_command_call_inner ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0), PM_ERR_RESCUE_MODIFIER_VALUE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#14 196.3 src/prism.c: In function ‘parse_expression_infix’:
#14 196.3 src/prism.c:21420:108: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *right = parse_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (parser->previous.type == PM_TOKEN_KEYWORD_AND ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0), PM_ERR_EXPECT_EXPRESSION_AFTER_OPERATOR, (uint16_t) (depth + 1));
#14 196.3                                                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#14 196.3 src/prism.c:21427:108: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *right = parse_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (parser->previous.type == PM_TOKEN_KEYWORD_OR ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0), PM_ERR_EXPECT_EXPRESSION_AFTER_OPERATOR, (uint16_t) (depth + 1));
#14 196.3                                                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#14 196.3 src/prism.c:21656:118: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *predicate = parse_value_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_IF_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                       ^
#14 196.3 src/prism.c:21663:118: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *predicate = parse_value_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_UNLESS_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                       ^
#14 196.3 src/prism.c:21671:118: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *predicate = parse_value_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_UNTIL_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                       ^
#14 196.3 src/prism.c:21679:118: error: conversion from ‘int’ to ‘uint8_t’ {aka ‘unsigned char’} may change value [-Werror=conversion]
#14 196.3              pm_node_t *predicate = parse_value_expression(parser, binding_power, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CONDITIONAL_WHILE_PREDICATE, (uint16_t) (depth + 1));
#14 196.3                                                                                                                       ^
#14 196.3 compiling build/shared/stringy.o

[Earlopain]

Ruby tests down to gcc 7, but 8 is only run with gcc 8.4.0, not 8.5.0. I wonder if that makes the difference

[eregon]

I guess it might be because of different compilation flags, this is using the flags from

prism/Makefile

Line 14 in 40ca8a4

CFLAGS := -g -O2 -std=c99 -Wall -Werror -Wextra -Wpedantic -Wundef -Wconversion -Wno-missing-braces -fPIC -fvisibility=hidden -Wimplicit-fallthrough $(CFLAGS)

but CRuby doesn't use that Makefile and likely has more relaxed flags like no -Werror or no -Wconversion.

Regarding more recent gcc not emitting this warnng is apparently because this family of warnings moved to -Warith-conversion according to ChatGPT, I'll test that theory, would be convenient to test locally.

[eregon]

Adding -Warith-conversion doesn't repro on gcc 15.2.1, I'll just look at the code and see if there is a reasonable fix then.

[eregon]

For the first warning on

prism/src/prism.c

Line 13891 in 40ca8a4

argument = parse_value_expression(parser, PM_BINDING_POWER_DEFINED, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | (!parsed_first_argument ? PM_PARSE_ACCEPTS_COMMAND_CALL : 0u) | PM_PARSE_ACCEPTS_LABEL, PM_ERR_EXPECT_ARGUMENT, (uint16_t) (depth + 1));

The issue seems to be that:

• 0u is not a uint8_t
• | in C promotes to int

So the real fix seems to be to cast the whole expression for the flags (and the first does not matter).

On

prism/src/prism.c

Line 17795 in 40ca8a4

predicate = parse_value_expression(parser, PM_BINDING_POWER_COMPOSITION, (flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL, PM_ERR_CASE_EXPRESSION_AFTER_CASE, (uint16_t) (depth + 1));

it is clear the | (or &) is what promotes to int as every operand is already uint8_t.
gcc doesn't mind flags & CONSTANT though so it seems to be OK with &.

This is already done in e.g.

prism/src/prism.c

Line 21792 in 40ca8a4

pm_node_t *value = parse_expression(parser, binding_power, (uint8_t) ((flags & PM_PARSE_ACCEPTS_DO_BLOCK) | PM_PARSE_ACCEPTS_COMMAND_CALL), PM_ERR_RESCUE_MODIFIER_VALUE, (uint16_t) (depth + 1));

So it seems good to solve it the same way.

[eregon]

For context, the reason we are using such an old gcc is to create truffleruby binaries that work on "any non-EOL Linux".