Declare the real FLAC block size in the synthesised STREAMINFO

src/libchdr_flac.c

@@ -248,8 +248,17 @@ int flac_decoder_reset(flac_decoder* decoder, uint32_t sample_rate, uint8_t num_
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  /* +2A: start of stream data */
 	};
 	memcpy(decoder->custom_header, s_header_template, sizeof(s_header_template));
-	decoder->custom_header[0x08] = decoder->custom_header[0x0a] = (block_size*num_channels) >> 8;
-	decoder->custom_header[0x09] = decoder->custom_header[0x0b] = (block_size*num_channels) & 0xff;
+	/* STREAMINFO counts inter-channel samples, so the block size goes in as
+	 * given - not multiplied by the channel count, which claimed twice the
+	 * real maximum for stereo and made dr_flac allocate a decoded-sample
+	 * buffer twice the size it needs. Over-declaring is otherwise harmless
+	 * (the value only sizes that buffer and rejects frames larger than it),
+	 * which is why this went unnoticed. The value is exact rather than
+	 * merely safe: the encoder picks its block size with the same function
+	 * the codecs here call to derive this argument. MAME's own decoder
+	 * writes block_size too. */
+	decoder->custom_header[0x08] = decoder->custom_header[0x0a] = block_size >> 8;
+	decoder->custom_header[0x09] = decoder->custom_header[0x0b] = block_size & 0xff;
 	decoder->custom_header[0x12] = sample_rate >> 12;
 	decoder->custom_header[0x13] = sample_rate >> 4;
 	decoder->custom_header[0x14] = (sample_rate << 4) | ((num_channels - 1) << 1);

tests/corpus/generate.sh

@@ -76,6 +76,11 @@ create_hd hd_lzma.chd       -c lzma
 create_hd hd_huff.chd       -c huff
 create_hd hd_zstd.chd       -c zstd
 create_hd hd_multi.chd      -c zlib,lzma,huff,zstd
+# The raw FLAC codec, on its own. hd_default happens to include flac hunks
+# because that is one of chdman's default hard-disk codecs, but relying on a
+# default to cover a codec is how a codec stops being covered - and the FLAC
+# decoder holds the largest per-instance buffer of any codec here.
+create_hd hd_flac.chd       -c flac
 
 # CD-ROM: default + per-codec.
 create_cd cd_default.chd

tests/rp2350-arm/check_budget.py

@@ -21,9 +21,11 @@
 	"hd_zstd": 200_000,
 	"hd_lzma": 80_000,
 	"hd_huff": 60_000,
+	"hd_flac": 100_000,
 	"cd_cdzl": 250_000,
 	"cd_cdzs": 400_000,
 	"cd_cdlz": 250_000,
+	"cd_cdfl": 250_000,
 }
 
 FAIL_RE = re.compile(r"^(\S+)\s+(?:OPEN|READ) FAILED: (.*)$")

tests/rp2350-arm/fw.c

@@ -23,9 +23,11 @@
 #include "embed/hd_zstd.h"
 #include "embed/hd_lzma.h"
 #include "embed/hd_huff.h"
+#include "embed/hd_flac.h"
 #include "embed/cd_cdzl.h"
 #include "embed/cd_cdzs.h"
 #include "embed/cd_cdlz.h"
+#include "embed/cd_cdfl.h"
 
 /* ---- malloc high-water-mark wrapper (linked via --wrap) ---- */
 
@@ -168,9 +170,11 @@ int main(void)
 	run_one("hd_zstd", hd_zstd_chd, hd_zstd_chd_len);
 	run_one("hd_lzma", hd_lzma_chd, hd_lzma_chd_len);
 	run_one("hd_huff", hd_huff_chd, hd_huff_chd_len);
+	run_one("hd_flac", hd_flac_chd, hd_flac_chd_len);
 	run_one("cd_cdzl", cd_cdzl_chd, cd_cdzl_chd_len);
 	run_one("cd_cdzs", cd_cdzs_chd, cd_cdzs_chd_len);
 	run_one("cd_cdlz", cd_cdlz_chd, cd_cdlz_chd_len);
+	run_one("cd_cdfl", cd_cdfl_chd, cd_cdfl_chd_len);
 	printf("=== done ===\n");
 	return 0;
 }

tests/rp2350-arm/gen_embed.sh

@@ -12,8 +12,10 @@ mkdir -p "$OUT_DIR"
 
 # One representative CHD per decompressor the RAM-budget check cares about:
 # every HD/raw codec (small hunks) plus every CD sub-codec (large hunks, the
-# ones that pay for a subcode decompressor on top of the base one).
-FILES=(hd_zlib hd_zstd hd_lzma hd_huff cd_cdzl cd_cdzs cd_cdlz)
+# ones that pay for a subcode decompressor on top of the base one). FLAC is in
+# the list because its decoder holds the largest per-instance buffer of any
+# codec here - leaving it out is how an oversized allocation went unnoticed.
+FILES=(hd_zlib hd_zstd hd_lzma hd_huff hd_flac cd_cdzl cd_cdzs cd_cdlz cd_cdfl)
 
 for f in "${FILES[@]}"; do
 	src="$SEEDS_DIR/${f}.chd"

tests/rp2350-riscv/check_budget.py

@@ -24,9 +24,11 @@
 	"hd_zstd": 200_000,
 	"hd_lzma": 80_000,
 	"hd_huff": 60_000,
+	"hd_flac": 100_000,
 	"cd_cdzl": 250_000,
 	"cd_cdzs": 400_000,
 	"cd_cdlz": 250_000,
+	"cd_cdfl": 250_000,
 }
 
 FAIL_RE = re.compile(r"^(\S+)\s+(?:OPEN|READ) FAILED: (.*)$")

tests/rp2350-riscv/fw.c

@@ -24,9 +24,11 @@
 #include "embed/hd_zstd.h"
 #include "embed/hd_lzma.h"
 #include "embed/hd_huff.h"
+#include "embed/hd_flac.h"
 #include "embed/cd_cdzl.h"
 #include "embed/cd_cdzs.h"
 #include "embed/cd_cdlz.h"
+#include "embed/cd_cdfl.h"
 
 /* ---- malloc high-water-mark wrapper (linked via --wrap) ---- */
 
@@ -169,9 +171,11 @@ int main(void)
 	run_one("hd_zstd", hd_zstd_chd, hd_zstd_chd_len);
 	run_one("hd_lzma", hd_lzma_chd, hd_lzma_chd_len);
 	run_one("hd_huff", hd_huff_chd, hd_huff_chd_len);
+	run_one("hd_flac", hd_flac_chd, hd_flac_chd_len);
 	run_one("cd_cdzl", cd_cdzl_chd, cd_cdzl_chd_len);
 	run_one("cd_cdzs", cd_cdzs_chd, cd_cdzs_chd_len);
 	run_one("cd_cdlz", cd_cdlz_chd, cd_cdlz_chd_len);
+	run_one("cd_cdfl", cd_cdfl_chd, cd_cdfl_chd_len);
 	printf("=== done ===\n");
 	return 0;
 }

tests/rp2350-riscv/gen_embed.sh

@@ -13,8 +13,10 @@ mkdir -p "$OUT_DIR"
 
 # One representative CHD per decompressor the RAM-budget check cares about:
 # every HD/raw codec (small hunks) plus every CD sub-codec (large hunks, the
-# ones that pay for a subcode decompressor on top of the base one).
-FILES=(hd_zlib hd_zstd hd_lzma hd_huff cd_cdzl cd_cdzs cd_cdlz)
+# ones that pay for a subcode decompressor on top of the base one). FLAC is in
+# the list because its decoder holds the largest per-instance buffer of any
+# codec here - leaving it out is how an oversized allocation went unnoticed.
+FILES=(hd_zlib hd_zstd hd_lzma hd_huff hd_flac cd_cdzl cd_cdzs cd_cdlz cd_cdfl)
 
 for f in "${FILES[@]}"; do
 	src="$SEEDS_DIR/${f}.chd"

tests/rv32/check_budget.py

@@ -19,9 +19,11 @@
 	"hd_zstd": 150_000,
 	"hd_lzma": 80_000,
 	"hd_huff": 200_000,
+	"hd_flac": 100_000,
 	"cd_cdzl": 200_000,
 	"cd_cdzs": 320_000,
 	"cd_cdlz": 200_000,
+	"cd_cdfl": 250_000,
 }
 
 FAIL_RE = re.compile(r"^(\S+)\s+(?:OPEN|READ) FAILED: (.*)$")

tests/rv32/fw.c

@@ -20,9 +20,11 @@
 #include "embed/hd_zstd.h"
 #include "embed/hd_lzma.h"
 #include "embed/hd_huff.h"
+#include "embed/hd_flac.h"
 #include "embed/cd_cdzl.h"
 #include "embed/cd_cdzs.h"
 #include "embed/cd_cdlz.h"
+#include "embed/cd_cdfl.h"
 
 /* ---- malloc high-water-mark wrapper (linked via --wrap) ---- */
 
@@ -165,9 +167,11 @@ int main(void)
 	run_one("hd_zstd", hd_zstd_chd, hd_zstd_chd_len);
 	run_one("hd_lzma", hd_lzma_chd, hd_lzma_chd_len);
 	run_one("hd_huff", hd_huff_chd, hd_huff_chd_len);
+	run_one("hd_flac", hd_flac_chd, hd_flac_chd_len);
 	run_one("cd_cdzl", cd_cdzl_chd, cd_cdzl_chd_len);
 	run_one("cd_cdzs", cd_cdzs_chd, cd_cdzs_chd_len);
 	run_one("cd_cdlz", cd_cdlz_chd, cd_cdlz_chd_len);
+	run_one("cd_cdfl", cd_cdfl_chd, cd_cdfl_chd_len);
 	printf("=== done ===\n");
 	return 0;
 }

tests/rv32/gen_embed.sh

@@ -12,8 +12,10 @@ mkdir -p "$OUT_DIR"
 
 # One representative CHD per decompressor the RAM-budget check cares about:
 # every HD/raw codec (small hunks) plus every CD sub-codec (large hunks, the
-# ones that pay for a subcode decompressor on top of the base one).
-FILES=(hd_zlib hd_zstd hd_lzma hd_huff cd_cdzl cd_cdzs cd_cdlz)
+# ones that pay for a subcode decompressor on top of the base one). FLAC is in
+# the list because its decoder holds the largest per-instance buffer of any
+# codec here - leaving it out is how an oversized allocation went unnoticed.
+FILES=(hd_zlib hd_zstd hd_lzma hd_huff hd_flac cd_cdzl cd_cdzs cd_cdlz cd_cdfl)
 
 for f in "${FILES[@]}"; do
 	src="$SEEDS_DIR/${f}.chd"