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[libc] Add nullptr check option to printf %s

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Some printf implementations perform a null check on pointers passed to
%s. While that's not in the standard, this patch adds it as an option
for compatibility. It also puts a similar check in %n behind the same
flag.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D156923
This commit is contained in:
Michael Jones 2023-08-02 10:53:52 -07:00
parent 07c8bcc21d
commit f6ba352988
4 changed files with 22 additions and 9 deletions
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2
libc/src/stdio/printf_core/printf_config.h
View File

@ -39,4 +39,6 @@
// TODO(michaelrj): Move the other printf configuration options into this file.
// LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_PRINTF_CONFIG_H

13
libc/src/stdio/printf_core/string_converter.h
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@ -22,9 +22,15 @@ namespace printf_core {
LIBC_INLINE int convert_string(Writer *writer, const FormatSection &to_conv) {
size_t string_len = 0;
const char *str_ptr = reinterpret_cast<const char *>(to_conv.conv_val_ptr);
for (char *cur_str = reinterpret_cast<char *>(to_conv.conv_val_ptr);
cur_str[string_len]; ++string_len) {
#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
if (str_ptr == nullptr) {
str_ptr = "null";
}
#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
for (const char *cur_str = (str_ptr); cur_str[string_len]; ++string_len) {
;
}
@ -42,8 +48,7 @@ LIBC_INLINE int convert_string(Writer *writer, const FormatSection &to_conv) {
RET_IF_RESULT_NEGATIVE(writer->write(' ', padding_spaces));
}
RET_IF_RESULT_NEGATIVE(writer->write(
{reinterpret_cast<const char *>(to_conv.conv_val_ptr), string_len}));
RET_IF_RESULT_NEGATIVE(writer->write({(str_ptr), string_len}));
// If the padding is on the right side, write the spaces last.
if (padding_spaces > 0 &&

8
libc/src/stdio/printf_core/write_int_converter.h
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@ -22,13 +22,11 @@ namespace printf_core {
LIBC_INLINE int convert_write_int(Writer *writer,
const FormatSection &to_conv) {
// This is an additional check added by LLVM-libc. The reason it returns -3 is
// because printf uses negative return values for errors, and -1 and -2 are
// already in use by the file_writer class for file errors.
// TODO: Remove this. It's better to crash than to provide an incorrect
// result.
#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
// This is an additional check added by LLVM-libc.
if (to_conv.conv_val_ptr == nullptr)
return NULLPTR_WRITE_ERROR;
#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
int written = writer->get_chars_written();

8
libc/test/src/stdio/sprintf_test.cpp
View File

@ -96,6 +96,12 @@ TEST(LlvmLibcSPrintfTest, StringConv) {
"isn't", 12, 10, "important. Ever.");
EXPECT_EQ(written, 26);
ASSERT_STREQ(buff, " beginning is important.");
#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
written = __llvm_libc::sprintf(buff, "%s", nullptr);
EXPECT_EQ(written, 4);
ASSERT_STREQ(buff, "null");
#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
}
TEST(LlvmLibcSPrintfTest, IntConv) {
@ -2781,8 +2787,10 @@ TEST(LlvmLibcSPrintfTest, WriteIntConv) {
EXPECT_EQ(test_val, 8);
ASSERT_STREQ(buff, "87654321");
#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
written = __llvm_libc::sprintf(buff, "abc123%n", nullptr);
EXPECT_LT(written, 0);
#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
}
#endif // LIBC_COPT_PRINTF_DISABLE_WRITE_INT